rfc9053.original.xml		rfc9053.xml
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	IETF" version="3" consensus="true">
	<!-- xml2rfc v2v3 conversion 2.24.0 -->
	<front>		<front>
	<title abbrev="COSE Algorithms">		<title abbrev="COSE Algorithms">CBOR Object Signing and Encryption (COSE): I
	CBOR Object Signing&nbsp;and&nbsp;Encryption&nbsp;(COSE): Initial Algorith		nitial Algorithms</title>
	ms		<seriesInfo name="RFC" value="9053" stream="IETF"/>
	</title>
	<seriesInfo name="Internet-Draft" value="draft-ietf-cose-rfc8152bis-algs-11"
	/>
	<author initials="J." surname="Schaad" fullname="Jim Schaad">		<author initials="J." surname="Schaad" fullname="Jim Schaad">
	<organization>August Cellars</organization>		<organization showOnFrontPage="true">August Cellars</organization>
	<address>		<address>
	<email>ietf@augustcellars.com</email>
	</address>		</address>
	</author>		</author>
	<date/>		<date month="08" year="2022"/>
	<area>Security</area>		<area>Security</area>
	<workgroup>COSE Working Group</workgroup>		<workgroup>COSE Working Group</workgroup>
	<abstract>		<keyword>Object Security</keyword>
	<t>		<keyword>COSE</keyword>
			<keyword>Constrained Devices</keyword>
			<keyword>AES</keyword>
			<keyword>AES-GCM</keyword>
			<keyword>AES-CCM</keyword>
			<keyword>ECDSA</keyword>
			<keyword>EdDSA</keyword>
			<keyword>ECC</keyword>
			<keyword>HSS-LMS</keyword>
			<keyword>AES-KW</keyword>
			<keyword>ECDH</keyword>
			<keyword>HMAC</keyword>
			<keyword>CMAC</keyword>
			<keyword>Cryptography</keyword>
			<abstract pn="section-abstract">
			<t indent="0" pn="section-abstract-1">
	Concise Binary Object Representation (CBOR) is a data format designed fo r small code size and small message size.		Concise Binary Object Representation (CBOR) is a data format designed fo r small code size and small message size.
	There is a need for the ability to have basic security services defined		There is a need to be able to define basic security services for this da
	for this data format.		ta format.
	THis document defines a set of algorithms that can be used with the CBOR		This document defines a set of algorithms that can be used with the
	Object Signing and Encryption (COSE) protocol RFC XXXX. <!-- <xref target="I-D.		CBOR Object Signing and Encryption (COSE) protocol (RFC 9052).
	ietf-cose-rfc8152bis-struct"/>.-->
	</t>		</t>
	</abstract>		<t indent="0" pn="section-abstract-2">
	<note removeInRFC="true">		This document, along with RFC 9052, obsoletes RFC 8152.
	<name>Contributing to this document</name>
	<!-- RFC EDITOR - Please remove this note before publishing -->
	<t>
	The source for this draft is being maintained in GitHub.
	Suggested changes should be submitted as pull requests at <eref target=
	"https://github.com/cose-wg/cose-rfc8152bis"/>.
	Instructions are on that page as well.
	Editorial changes can be managed in GitHub, but any substantial issues n
	eed to be discussed on the COSE mailing list.
	</t>		</t>
	</note>		</abstract>
			<boilerplate>
			<section anchor="status-of-memo" numbered="false" removeInRFC="false" toc=
			"exclude" pn="section-boilerplate.1">
			<name slugifiedName="name-status-of-this-memo">Status of This Memo</name
			>
			<t indent="0" pn="section-boilerplate.1-1">
			This document is not an Internet Standards Track specification; it i
			s
			published for informational purposes.
			</t>
			<t indent="0" pn="section-boilerplate.1-2">
			This document is a product of the Internet Engineering Task Force
			(IETF). It represents the consensus of the IETF community. It has
			received public review and has been approved for publication by the
			Internet Engineering Steering Group (IESG). Not all documents
			approved by the IESG are candidates for any level of Internet
			Standard; see Section 2 of RFC 7841.
			</t>
			<t indent="0" pn="section-boilerplate.1-3">
			Information about the current status of this document, any
			errata, and how to provide feedback on it may be obtained at
			<eref target="https://www.rfc-editor.org/info/rfc9053" brackets="non
			e"/>.
			</t>
			</section>
			<section anchor="copyright" numbered="false" removeInRFC="false" toc="excl
			ude" pn="section-boilerplate.2">
			<name slugifiedName="name-copyright-notice">Copyright Notice</name>
			<t indent="0" pn="section-boilerplate.2-1">
			Copyright (c) 2022 IETF Trust and the persons identified as the
			document authors. All rights reserved.
			</t>
			<t indent="0" pn="section-boilerplate.2-2">
			This document is subject to BCP 78 and the IETF Trust's Legal
			Provisions Relating to IETF Documents
			(<eref target="https://trustee.ietf.org/license-info" brackets="none
			"/>) in effect on the date of
			publication of this document. Please review these documents
			carefully, as they describe your rights and restrictions with
			respect to this document. Code Components extracted from this
			document must include Revised BSD License text as described in
			Section 4.e of the Trust Legal Provisions and are provided without
			warranty as described in the Revised BSD License.
			</t>
			</section>
			</boilerplate>
			<toc>
			<section anchor="toc" numbered="false" removeInRFC="false" toc="exclude" p
			n="section-toc.1">
			<name slugifiedName="name-table-of-contents">Table of Contents</name>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="section-to
			c.1-1">
			<li pn="section-toc.1-1.1">
			<t indent="0" pn="section-toc.1-1.1.1"><xref derivedContent="1" form
			at="counter" sectionFormat="of" target="section-1"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-introduction">Introduction</xref><
			/t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.1.2">
			<li pn="section-toc.1-1.1.2.1">
			<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.1.1"><
			xref derivedContent="1.1" format="counter" sectionFormat="of" target="section-1.
			1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-re
			quirements-terminology">Requirements Terminology</xref></t>
			</li>
			<li pn="section-toc.1-1.1.2.2">
			<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.2.1"><
			xref derivedContent="1.2" format="counter" sectionFormat="of" target="section-1.
			2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ch
			anges-from-rfc-8152">Changes from RFC 8152</xref></t>
			</li>
			<li pn="section-toc.1-1.1.2.3">
			<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.3.1"><
			xref derivedContent="1.3" format="counter" sectionFormat="of" target="section-1.
			3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-do
			cument-terminology">Document Terminology</xref></t>
			</li>
			<li pn="section-toc.1-1.1.2.4">
			<t indent="0" pn="section-toc.1-1.1.2.4.1"><xref derivedContent=
			"1.4" format="counter" sectionFormat="of" target="section-1.4"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-cddl-grammar-for-cbor-
			data-">CDDL Grammar for CBOR Data Structures</xref></t>
			</li>
			<li pn="section-toc.1-1.1.2.5">
			<t indent="0" pn="section-toc.1-1.1.2.5.1"><xref derivedContent=
			"1.5" format="counter" sectionFormat="of" target="section-1.5"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-examples">Examples</xr
			ef></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.2">
			<t indent="0" pn="section-toc.1-1.2.1"><xref derivedContent="2" form
			at="counter" sectionFormat="of" target="section-2"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-signature-algorithms">Signature Al
			gorithms</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.2.2">
			<li pn="section-toc.1-1.2.2.1">
			<t indent="0" pn="section-toc.1-1.2.2.1.1"><xref derivedContent=
			"2.1" format="counter" sectionFormat="of" target="section-2.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-ecdsa">ECDSA</xref></t
			>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.2.2.1.2">
			<li pn="section-toc.1-1.2.2.1.2.1">
			<t indent="0" pn="section-toc.1-1.2.2.1.2.1.1"><xref derived
			Content="2.1.1" format="counter" sectionFormat="of" target="section-2.1.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-security-c
			onsiderations-for">Security Considerations for ECDSA</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.2.2.2">
			<t indent="0" pn="section-toc.1-1.2.2.2.1"><xref derivedContent=
			"2.2" format="counter" sectionFormat="of" target="section-2.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-edwards-curve-digital-
			signa">Edwards-Curve Digital Signature Algorithm (EdDSA)</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.2.2.2.2">
			<li pn="section-toc.1-1.2.2.2.2.1">
			<t indent="0" pn="section-toc.1-1.2.2.2.2.1.1"><xref derived
			Content="2.2.1" format="counter" sectionFormat="of" target="section-2.2.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-security-c
			onsiderations-for-">Security Considerations for EdDSA</xref></t>
			</li>
			</ul>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.3">
			<t indent="0" pn="section-toc.1-1.3.1"><xref derivedContent="3" form
			at="counter" sectionFormat="of" target="section-3"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-message-authentication-code">Messa
			ge Authentication Code (MAC) Algorithms</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.3.2">
			<li pn="section-toc.1-1.3.2.1">
			<t indent="0" pn="section-toc.1-1.3.2.1.1"><xref derivedContent=
			"3.1" format="counter" sectionFormat="of" target="section-3.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-hash-based-message-aut
			henti">Hash-Based Message Authentication Codes (HMACs)</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.3.2.1.2">
			<li pn="section-toc.1-1.3.2.1.2.1">
			<t indent="0" pn="section-toc.1-1.3.2.1.2.1.1"><xref derived
			Content="3.1.1" format="counter" sectionFormat="of" target="section-3.1.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-security-c
			onsiderations-for-h">Security Considerations for HMAC</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.3.2.2">
			<t indent="0" pn="section-toc.1-1.3.2.2.1"><xref derivedContent=
			"3.2" format="counter" sectionFormat="of" target="section-3.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-aes-message-authentica
			tion-">AES Message Authentication Code (AES-CBC-MAC)</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.3.2.2.2">
			<li pn="section-toc.1-1.3.2.2.2.1">
			<t indent="0" pn="section-toc.1-1.3.2.2.2.1.1"><xref derived
			Content="3.2.1" format="counter" sectionFormat="of" target="section-3.2.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-security-c
			onsiderations-for-a">Security Considerations for AES-CBC-MAC </xref></t>
			</li>
			</ul>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.4">
			<t indent="0" pn="section-toc.1-1.4.1"><xref derivedContent="4" form
			at="counter" sectionFormat="of" target="section-4"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-content-encryption-algorith">Conte
			nt Encryption Algorithms</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.4.2">
			<li pn="section-toc.1-1.4.2.1">
			<t indent="0" pn="section-toc.1-1.4.2.1.1"><xref derivedContent=
			"4.1" format="counter" sectionFormat="of" target="section-4.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-aes-gcm">AES-GCM</xref
			></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.4.2.1.2">
			<li pn="section-toc.1-1.4.2.1.2.1">
			<t indent="0" pn="section-toc.1-1.4.2.1.2.1.1"><xref derived
			Content="4.1.1" format="counter" sectionFormat="of" target="section-4.1.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-security-c
			onsiderations-for-ae">Security Considerations for AES-GCM</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.4.2.2">
			<t indent="0" pn="section-toc.1-1.4.2.2.1"><xref derivedContent=
			"4.2" format="counter" sectionFormat="of" target="section-4.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-aes-ccm">AES-CCM</xref
			></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.4.2.2.2">
			<li pn="section-toc.1-1.4.2.2.2.1">
			<t indent="0" pn="section-toc.1-1.4.2.2.2.1.1"><xref derived
			Content="4.2.1" format="counter" sectionFormat="of" target="section-4.2.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-security-c
			onsiderations-for-aes">Security Considerations for AES-CCM</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.4.2.3">
			<t indent="0" pn="section-toc.1-1.4.2.3.1"><xref derivedContent=
			"4.3" format="counter" sectionFormat="of" target="section-4.3"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-chacha20-and-poly1305"
			>ChaCha20 and Poly1305</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.4.2.3.2">
			<li pn="section-toc.1-1.4.2.3.2.1">
			<t indent="0" pn="section-toc.1-1.4.2.3.2.1.1"><xref derived
			Content="4.3.1" format="counter" sectionFormat="of" target="section-4.3.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-security-c
			onsiderations-for-c">Security Considerations for ChaCha20/Poly1305</xref></t>
			</li>
			</ul>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.5">
			<t indent="0" pn="section-toc.1-1.5.1"><xref derivedContent="5" form
			at="counter" sectionFormat="of" target="section-5"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-key-derivation-functions-kd">Key D
			erivation Functions (KDFs)</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.5.2">
			<li pn="section-toc.1-1.5.2.1">
			<t indent="0" pn="section-toc.1-1.5.2.1.1"><xref derivedContent=
			"5.1" format="counter" sectionFormat="of" target="section-5.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-hmac-based-extract-and
			-expa">HMAC-Based Extract-and-Expand Key Derivation Function (HKDF)</xref></t>
			</li>
			<li pn="section-toc.1-1.5.2.2">
			<t indent="0" pn="section-toc.1-1.5.2.2.1"><xref derivedContent=
			"5.2" format="counter" sectionFormat="of" target="section-5.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-context-information-st
			ructu">Context Information Structure</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.6">
			<t indent="0" pn="section-toc.1-1.6.1"><xref derivedContent="6" form
			at="counter" sectionFormat="of" target="section-6"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-content-key-distribution-me">Conte
			nt Key Distribution Methods</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.6.2">
			<li pn="section-toc.1-1.6.2.1">
			<t indent="0" pn="section-toc.1-1.6.2.1.1"><xref derivedContent=
			"6.1" format="counter" sectionFormat="of" target="section-6.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-direct-encryption">Dir
			ect Encryption</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.6.2.1.2">
			<li pn="section-toc.1-1.6.2.1.2.1">
			<t indent="0" pn="section-toc.1-1.6.2.1.2.1.1"><xref derived
			Content="6.1.1" format="counter" sectionFormat="of" target="section-6.1.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-direct-key
			">Direct Key</xref></t>
			</li>
			<li pn="section-toc.1-1.6.2.1.2.2">
			<t indent="0" pn="section-toc.1-1.6.2.1.2.2.1"><xref derived
			Content="6.1.2" format="counter" sectionFormat="of" target="section-6.1.2"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-direct-key
			-with-kdf">Direct Key with KDF</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.6.2.2">
			<t indent="0" pn="section-toc.1-1.6.2.2.1"><xref derivedContent=
			"6.2" format="counter" sectionFormat="of" target="section-6.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-key-wrap">Key Wrap</xr
			ef></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.6.2.2.2">
			<li pn="section-toc.1-1.6.2.2.2.1">
			<t indent="0" pn="section-toc.1-1.6.2.2.2.1.1"><xref derived
			Content="6.2.1" format="counter" sectionFormat="of" target="section-6.2.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-aes-key-wr
			ap">AES Key Wrap</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.6.2.3">
			<t indent="0" pn="section-toc.1-1.6.2.3.1"><xref derivedContent=
			"6.3" format="counter" sectionFormat="of" target="section-6.3"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-direct-key-agreement">
			Direct Key Agreement</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.6.2.3.2">
			<li pn="section-toc.1-1.6.2.3.2.1">
			<t indent="0" pn="section-toc.1-1.6.2.3.2.1.1"><xref derived
			Content="6.3.1" format="counter" sectionFormat="of" target="section-6.3.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-direct-ecd
			h">Direct ECDH</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.6.2.4">
			<t indent="0" pn="section-toc.1-1.6.2.4.1"><xref derivedContent=
			"6.4" format="counter" sectionFormat="of" target="section-6.4"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-key-agreement-with-key
			-wrap">Key Agreement with Key Wrap</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.6.2.4.2">
			<li pn="section-toc.1-1.6.2.4.2.1">
			<t indent="0" pn="section-toc.1-1.6.2.4.2.1.1"><xref derived
			Content="6.4.1" format="counter" sectionFormat="of" target="section-6.4.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-ecdh-with-
			key-wrap">ECDH with Key Wrap</xref></t>
			</li>
			</ul>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.7">
			<t indent="0" pn="section-toc.1-1.7.1"><xref derivedContent="7" form
			at="counter" sectionFormat="of" target="section-7"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-key-object-parameters">Key Object
			Parameters</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.7.2">
			<li pn="section-toc.1-1.7.2.1">
			<t indent="0" pn="section-toc.1-1.7.2.1.1"><xref derivedContent=
			"7.1" format="counter" sectionFormat="of" target="section-7.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-elliptic-curve-keys">E
			lliptic Curve Keys</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
			ction-toc.1-1.7.2.1.2">
			<li pn="section-toc.1-1.7.2.1.2.1">
			<t indent="0" pn="section-toc.1-1.7.2.1.2.1.1"><xref derived
			Content="7.1.1" format="counter" sectionFormat="of" target="section-7.1.1"/>.  <
			xref derivedContent="" format="title" sectionFormat="of" target="name-double-coo
			rdinate-curves">Double Coordinate Curves</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.7.2.2">
			<t indent="0" pn="section-toc.1-1.7.2.2.1"><xref derivedContent=
			"7.2" format="counter" sectionFormat="of" target="section-7.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-octet-key-pair">Octet
			Key Pair</xref></t>
			</li>
			<li pn="section-toc.1-1.7.2.3">
			<t indent="0" pn="section-toc.1-1.7.2.3.1"><xref derivedContent=
			"7.3" format="counter" sectionFormat="of" target="section-7.3"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-symmetric-keys">Symmet
			ric Keys</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.8">
			<t indent="0" pn="section-toc.1-1.8.1"><xref derivedContent="8" form
			at="counter" sectionFormat="of" target="section-8"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-cose-capabilities">COSE Capabiliti
			es</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.8.2">
			<li pn="section-toc.1-1.8.2.1">
			<t indent="0" pn="section-toc.1-1.8.2.1.1"><xref derivedContent=
			"8.1" format="counter" sectionFormat="of" target="section-8.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-assignments-for-existi
			ng-al">Assignments for Existing Algorithms</xref></t>
			</li>
			<li pn="section-toc.1-1.8.2.2">
			<t indent="0" pn="section-toc.1-1.8.2.2.1"><xref derivedContent=
			"8.2" format="counter" sectionFormat="of" target="section-8.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-assignments-for-existi
			ng-ke">Assignments for Existing Key Types</xref></t>
			</li>
			<li pn="section-toc.1-1.8.2.3">
			<t indent="0" pn="section-toc.1-1.8.2.3.1"><xref derivedContent=
			"8.3" format="counter" sectionFormat="of" target="section-8.3"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-examples-2">Examples</
			xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.9">
			<t indent="0" pn="section-toc.1-1.9.1"><xref derivedContent="9" form
			at="counter" sectionFormat="of" target="section-9"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-cbor-encoding-restrictions">CBOR E
			ncoding Restrictions</xref></t>
			</li>
			<li pn="section-toc.1-1.10">
			<t indent="0" pn="section-toc.1-1.10.1"><xref derivedContent="10" fo
			rmat="counter" sectionFormat="of" target="section-10"/>. <xref derivedContent=""
			format="title" sectionFormat="of" target="name-iana-considerations">IANA Consid
			erations</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.10.2">
			<li pn="section-toc.1-1.10.2.1">
			<t indent="0" pn="section-toc.1-1.10.2.1.1"><xref derivedContent
			="10.1" format="counter" sectionFormat="of" target="section-10.1"/>.  <xref deri
			vedContent="" format="title" sectionFormat="of" target="name-changes-to-the-cose
			-key-typ">Changes to the "COSE Key Types" Registry</xref></t>
			</li>
			<li pn="section-toc.1-1.10.2.2">
			<t indent="0" pn="section-toc.1-1.10.2.2.1"><xref derivedContent
			="10.2" format="counter" sectionFormat="of" target="section-10.2"/>.  <xref deri
			vedContent="" format="title" sectionFormat="of" target="name-changes-to-the-cose
			-algorit">Changes to the "COSE Algorithms" Registry</xref></t>
			</li>
			<li pn="section-toc.1-1.10.2.3">
			<t indent="0" pn="section-toc.1-1.10.2.3.1"><xref derivedContent
			="10.3" format="counter" sectionFormat="of" target="section-10.3"/>.  <xref deri
			vedContent="" format="title" sectionFormat="of" target="name-changes-to-the-cose
			-key-type">Changes to the "COSE Key Type Parameters" Registry</xref></t>
			</li>
			<li pn="section-toc.1-1.10.2.4">
			<t indent="0" pn="section-toc.1-1.10.2.4.1"><xref derivedContent
			="10.4" format="counter" sectionFormat="of" target="section-10.4"/>.  <xref deri
			vedContent="" format="title" sectionFormat="of" target="name-expert-review-instr
			uctions">Expert Review Instructions</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.11">
			<t indent="0" pn="section-toc.1-1.11.1"><xref derivedContent="11" fo
			rmat="counter" sectionFormat="of" target="section-11"/>. <xref derivedContent=""
			format="title" sectionFormat="of" target="name-security-considerations">Securit
			y Considerations</xref></t>
			</li>
			<li pn="section-toc.1-1.12">
			<t indent="0" pn="section-toc.1-1.12.1"><xref derivedContent="12" fo
			rmat="counter" sectionFormat="of" target="section-12"/>. <xref derivedContent=""
			format="title" sectionFormat="of" target="name-references">References</xref></t
			>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.12.2">
			<li pn="section-toc.1-1.12.2.1">
			<t indent="0" pn="section-toc.1-1.12.2.1.1"><xref derivedContent
			="12.1" format="counter" sectionFormat="of" target="section-12.1"/>.  <xref deri
			vedContent="" format="title" sectionFormat="of" target="name-normative-reference
			s">Normative References</xref></t>
			</li>
			<li pn="section-toc.1-1.12.2.2">
			<t indent="0" pn="section-toc.1-1.12.2.2.1"><xref derivedContent
			="12.2" format="counter" sectionFormat="of" target="section-12.2"/>.  <xref deri
			vedContent="" format="title" sectionFormat="of" target="name-informative-referen
			ces">Informative References</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.13">
			<t indent="0" pn="section-toc.1-1.13.1"><xref derivedContent="" form
			at="none" sectionFormat="of" target="section-appendix.a"/><xref derivedContent="
			" format="title" sectionFormat="of" target="name-acknowledgments">Acknowledgment
			s</xref></t>
			</li>
			<li pn="section-toc.1-1.14">
			<t indent="0" pn="section-toc.1-1.14.1"><xref derivedContent="" form
			at="none" sectionFormat="of" target="section-appendix.b"/><xref derivedContent="
			" format="title" sectionFormat="of" target="name-authors-address">Author's Addre
			ss</xref></t>
			</li>
			</ul>
			</section>
			</toc>
	</front>		</front>
	<middle>		<middle>
	<section anchor="introduction">		<section anchor="introduction" numbered="true" removeInRFC="false" toc="incl
			ude" pn="section-1">
	<name>Introduction</name>		<name slugifiedName="name-introduction">Introduction</name>
	<t>		<t indent="0" pn="section-1-1">
	There has been an increased focus on small, constrained devices that mak e up the Internet of Things (IoT).		There has been an increased focus on small, constrained devices that mak e up the Internet of Things (IoT).
	One of the standards that has come out of this process is "Concise Binar		One of the standards that has come out of this process is "Concise
	y Object Representation (CBOR)" <xref target="RFC7049"/>.		Binary Object Representation (CBOR)" <xref target="STD94" format="default
	CBOR extended the data model of JavaScript Object Notation (JSON) <xref		" sectionFormat="of" derivedContent="STD94"/>.
	target="STD90"/> by allowing for binary data, among other changes.		CBOR extended the data model of JavaScript Object Notation (JSON)
	CBOR is being adopted by several of the IETF working groups dealing with		<xref target="STD90" format="default" sectionFormat="of" derivedContent="
	the IoT world as their encoding of data structures.		STD90"/> by allowing for binary data, among other
	CBOR was designed specifically to be both small in terms of messages tra		changes.
	nsported and implementation size and be a schema-free decoder.		CBOR has been adopted by several of the IETF working groups dealing
	A need exists to provide message security services for IoT, and using CB		with the IoT world as their method of encoding data structures.
	OR as the message-encoding format makes sense.		CBOR was designed specifically to be small in terms of both messages
			transported and implementation size and to have a schema-free decoder.
			A need exists to provide message security services for IoT, and using
			CBOR as the message-encoding format makes sense.
	</t>		</t>
	<t>		<t indent="0" pn="section-1-2">
	The core COSE specification consists of two documents.		The core COSE specification consists of two documents.
	<xref target="I-D.ietf-cose-rfc8152bis-struct"/> contains the serializat ion structures and the procedures for using the different cryptographic algorith ms.		<xref target="RFC9052" format="default" sectionFormat="of" derivedConten t="RFC9052"/> contains the serialization structures and the procedures for using the different cryptographic algorithms.
	This document provides an initial set of algorithms for use with those s tructures.		This document provides an initial set of algorithms for use with those s tructures.
	</t>		</t>
	<section anchor="requirements-terminology">		<section anchor="requirements-terminology" numbered="true" removeInRFC="fa
			lse" toc="include" pn="section-1.1">
	<name>Requirements Terminology</name>		<name slugifiedName="name-requirements-terminology">Requirements Termino
	<t>		logy</name>
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL		<t indent="0" pn="section-1.1-1">
	NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",		The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp1
	"MAY", and "OPTIONAL" in this document are to be interpreted as		4>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14
	described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/>		>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<b
	when, and only when, they		cp14>NOT RECOMMENDED</bcp14>",
			"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document a
			re to be interpreted as
			described in BCP 14 <xref target="RFC2119" format="default" sectionFor
			mat="of" derivedContent="RFC2119"/> <xref target="RFC8174" format="default" sect
			ionFormat="of" derivedContent="RFC8174"/> when, and only when, they
	appear in all capitals, as shown here.		appear in all capitals, as shown here.
	</t>		</t>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-1.2
			">
	<name>Changes from RFC8152</name>		<name slugifiedName="name-changes-from-rfc-8152">Changes from RFC 8152</
			name>
	<ul>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-1
			.2-1">
	<li>		<li pn="section-1.2-1.1">
	Extract the sections dealing with specific algorithms into this do		Extracted the sections dealing with specific algorithms and placed
	cument.		them into this document.
	The sections dealing with structure and general processing rules a		The sections dealing with structure and general processing rules
	re placed in <xref target="I-D.ietf-cose-rfc8152bis-struct"/>.		are placed in <xref target="RFC9052" format="default" sectionFormat
			="of" derivedContent="RFC9052"/>.
	</li>		</li>
	<li>Text clarifications and changes in terminology.</li>		<li pn="section-1.2-1.2">Made text clarifications and changes in termi
			nology.</li>
			<li pn="section-1.2-1.3">Removed all of the details relating to counte
			rsignatures and placed them in <xref target="I-D.ietf-cose-countersign" format="
			default" sectionFormat="of" derivedContent="COUNTERSIGN"/>.</li>
	</ul>		</ul>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-1.3
			">
	<name>Document Terminology</name>		<name slugifiedName="name-document-terminology">Document Terminology</na
	<t>In this document, we use the following terminology: </t>		me>
	<t>Byte is a synonym for octet.</t>		<t indent="0" pn="section-1.3-1">In this document, we use the following
	<t>Constrained Application Protocol (CoAP) is a specialized web transfer		terminology: </t>
	protocol for use in constrained systems. It is defined in <xref target="RFC725		<dl indent="3" newline="false" spacing="normal" pn="section-1.3-2">
	2"/>. </t>		<dt pn="section-1.3-2.1">Byte:</dt>
	<t>		<dd pn="section-1.3-2.2">A synonym for octet.</dd>
	Authenticated Encryption (AE) <xref target="RFC5116"/> algorithms are		<dt pn="section-1.3-2.3">Constrained Application Protocol (CoAP):</dt>
	encryption algorithms that provide an authentication check of the contents with		<dd pn="section-1.3-2.4">A specialized
	the encryption service.		web transfer protocol for use in constrained systems. It is defined
	An example of an AE algorithm used in COSE is AES Key Wrap <xref targe		in <xref target="RFC7252" format="default" sectionFormat="of" derivedCont
	t="RFC3394"/>.		ent="RFC7252"/>.</dd>
	These algorithms are used for key encryption algorithms, but AEAD algo		<dt pn="section-1.3-2.5">Authenticated Encryption (AE) algorithms <xre
	rithms would be preferred.		f target="RFC5116" format="default" sectionFormat="of" derivedContent="RFC5116"/
	</t>		>:
	<t>		</dt>
	Authenticated Encryption with Associated Data (AEAD) <xref target="RFC		<dd pn="section-1.3-2.6">Encryption algorithms that provide an
	5116"/> algorithms provide the same authentication service of the content as AE		authentication check of the contents along with the encryption service.
	algorithms do.		An example of an AE algorithm used in COSE is AES Key Wrap <xref targe
	They also allow for associated data to be included in the authenticati		t="RFC3394" format="default" sectionFormat="of" derivedContent="RFC3394"/>.
	on service, but which is not part of the encrypted body.		These algorithms are used for key encryption, but
	An example of an AEAD algorithm used in COSE is AES-GCM <xref target="		Authenticated Encryption with Associated Data (AEAD)
	RFC5116"/>.		algorithms would be preferred.
	These algorithms are used for content encryption and can be used for k		</dd>
	ey encryption as well.		<dt pn="section-1.3-2.7">AEAD algorithms <xref target="RFC5116" format
	</t>		="default" sectionFormat="of" derivedContent="RFC5116"/>:</dt>
	<t>The term 'byte string' is used for sequences of bytes, while the term		<dd pn="section-1.3-2.8">Encryption algorithms that provide the same a
	'text string' is used for sequences of characters.</t>		uthentication service of
			the content as AE algorithms do, and also allow
	<t>		associated data that is not part of the encrypted body to be included
			in the authentication service. An example of an AEAD
			algorithm used in COSE is AES-GCM <xref target="RFC5116" format="default"
			sectionFormat="of" derivedContent="RFC5116"/>. These
			algorithms are used for content encryption and can be used for key
			encryption as well.
			</dd>
			</dl>
			<t indent="0" pn="section-1.3-3">The term "byte string" is used for sequ
			ences of bytes, while the term "text string" is used for sequences of characters
			.</t>
			<t indent="0" pn="section-1.3-4">
	The tables for algorithms contain the following columns:		The tables for algorithms contain the following columns:
	</t>		</t>
	<ul>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-1
	<li>A name for use in documents for the algorithms.</li>		.3-5">
	<li>		<li pn="section-1.3-5.1">A name for the algorithm for use in documents
			.</li>
			<li pn="section-1.3-5.2">
	The value used on the wire for the algorithm.		The value used on the wire for the algorithm.
	One place this is used is the algorithm header parameter of a messag e.		One place this is used is the algorithm header parameter of a messag e.
	</li>		</li>
	<li>A short description so that the algorithm can be easily identified when scanning the IANA registry.</li>		<li pn="section-1.3-5.3">A short description so that the algorithm can be easily identified when scanning the IANA registry.</li>
	</ul>		</ul>
	<t>		<t indent="0" pn="section-1.3-6">
	Additional columns may be present in the table depending on the algori		Additional columns may be present in a table depending on the
	thms.		algorithms.
	</t>		</t>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-1.4
			">
	<name>CBOR Grammar</name>		<name slugifiedName="name-cddl-grammar-for-cbor-data-">CDDL Grammar for
	<t>		CBOR Data Structures</name>
	At the time that <xref target="RFC8152"/> was initially published, the		<t indent="0" pn="section-1.4-1">
	CBOR Data Definition Language (CDDL) <xref target="RFC8610"/> had not yet been		When COSE was originally written, the Concise Data Definition
	published.		Language (CDDL) <xref target="RFC8610" format="default" sectionFormat=
	This document uses a variant of CDDL which is described in <xref targe		"of" derivedContent="RFC8610"/> had not yet been published
	t="I-D.ietf-cose-rfc8152bis-struct"/>.		in an RFC, so it could not be used as the data description
			language to normatively describe the CBOR data structures employed
			by COSE.
			For that reason, the CBOR data objects defined here are described
			in prose.
			Additional (non-normative) descriptions of the
			COSE data objects are provided in a subset of CDDL, described in
			<xref target="RFC9052" format="default" sectionFormat="of" derivedCont
			ent="RFC9052"/>.
	</t>		</t>
	</section>		</section>
	<section anchor="examples">		<section anchor="examples" numbered="true" removeInRFC="false" toc="includ
			e" pn="section-1.5">
	<name>Examples</name>		<name slugifiedName="name-examples">Examples</name>
	<t>		<t indent="0" pn="section-1.5-1">
	A GitHub project has been created at <xref target="GitHub-Examples"/>		A GitHub project has been created at <xref target="GitHub-Examples" fo
	that contains a set of testing examples as well.		rmat="default" sectionFormat="of" derivedContent="GitHub-Examples"/> that contai
			ns a set of testing examples.
	Each example is found in a JSON file that contains the inputs used to create the example, some of the intermediate values that can be used for debuggi ng, and the output of the example.		Each example is found in a JSON file that contains the inputs used to create the example, some of the intermediate values that can be used for debuggi ng, and the output of the example.
	The results are encoded using both hexadecimal and CBOR diagnostic not		The results are encoded using both hexadecimal and
	ation format.		CBOR diagnostic notation format.
	</t>		</t>
	<t>		<t indent="0" pn="section-1.5-2">
	Some of the examples are designed to test failure case; these are clea		Some of the examples are designed to be failure-testing cases; these
	rly marked as such in the JSON file.		are clearly marked as such in the JSON file.
	If errors in the examples in this document are found, the examples on
	GitHub will be updated, and a note to that effect will be placed in the JSON fil
	e.
	</t>		</t>
	</section>		</section>
	</section>		</section>
			<section anchor="SigAlgs" numbered="true" removeInRFC="false" toc="include"
	<section anchor="SigAlgs">		pn="section-2">
			<name slugifiedName="name-signature-algorithms">Signature Algorithms</name
	<name>Signature Algorithms</name>		>
	<t>		<t indent="0" pn="section-2-1">
	<relref section="&SigSection;" target="I-D.ietf-cose-rfc8152bis-struct"/		<xref section="8.1" target="RFC9052" sectionFormat="of" format="default"
	> contains a generic description of signature algorithms.		derivedLink="https://rfc-editor.org/rfc/rfc9052#section-8.1" derivedContent="RF
	The document defines signature algorithm identifiers for two signature a		C9052"/> contains a generic description of signature algorithms.
	lgorithms.		This document defines signature algorithm identifiers for two signature
			algorithms.
	</t>		</t>
	<section anchor="ECDSA">		<section anchor="ECDSA" numbered="true" removeInRFC="false" toc="include"
			pn="section-2.1">
	<name>ECDSA</name>		<name slugifiedName="name-ecdsa">ECDSA</name>
	<t>ECDSA <xref target="DSS"/> defines a signature algorithm using ECC.		<t indent="0" pn="section-2.1-1">The Elliptic Curve Digital Signature Al
	Implementations <bcp14>SHOULD</bcp14> use a deterministic version of ECDSA such		gorithm (ECDSA) <xref target="DSS" format="default" sectionFormat="of" derivedCo
	as the one defined in <xref target="RFC6979"/>. The use of a deterministic sign		ntent="DSS"/> defines a signature algorithm using Elliptic Curve Cryptography (E
	ature algorithm allows for systems to avoid relying on random number generators		CC).
	in order to avoid generating the same value of 'k' (the per-message random value		Implementations <bcp14>SHOULD</bcp14> use a deterministic version of
	). Biased generation of the value 'k' can be attacked, and collisions of this va		ECDSA such as the one defined in <xref target="RFC6979" format="default"
	lue leads to leaked keys. It additionally allows for doing deterministic tests		sectionFormat="of" derivedContent="RFC6979"/>. The use of
	for the signature algorithm. The use of deterministic ECDSA does not lessen the		a deterministic signature algorithm allows systems to avoid relying on
	need to have good random number generation when creating the private key. </t>		random number generators in order to avoid generating the same value
	<t>The ECDSA signature algorithm is parameterized with a hash function (		of "k" (the per-message random value). Biased generation of the value
	h). In the event that the length of the hash function output is greater than th		"k" can be attacked, and collisions of this value lead to leaked
	e group of the key, the leftmost bytes of the hash output are used. </t>		keys. It additionally allows performing deterministic tests for the
	<t>The algorithms defined in this document can be found in <xref target=		signature algorithm. The use of deterministic ECDSA does not lessen
	"x-table_ecdsa"/>. </t>		the need to have good random number generation when creating the
	<table anchor="x-table_ecdsa" align="center">		private key. </t>
			<t indent="0" pn="section-2.1-2">The ECDSA signature algorithm is parame
	<name>ECDSA Algorithm Values</name>		terized with a hash function
			(h). In the event that the length of the hash function output is
			greater than the group of the key, the leftmost bytes of the hash
			output are used. </t>
			<t indent="0" pn="section-2.1-3">The algorithms defined in this document
			can be found in <xref target="x-table_ecdsa" format="default" sectionFormat="of
			" derivedContent="Table 1"/>. </t>
			<table anchor="x-table_ecdsa" align="center" pn="table-1">
			<name slugifiedName="name-ecdsa-algorithm-values">ECDSA Algorithm Valu
			es</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Hash</th>		<th align="left" colspan="1" rowspan="1">Hash</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>ES256</td>		<td align="left" colspan="1" rowspan="1">ES256</td>
	<td>-7</td>		<td align="center" colspan="1" rowspan="1">-7</td>
	<td>SHA-256</td>		<td align="left" colspan="1" rowspan="1">SHA-256</td>
	<td>ECDSA w/ SHA-256</td>		<td align="left" colspan="1" rowspan="1">ECDSA w/ SHA-256</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>ES384</td>		<td align="left" colspan="1" rowspan="1">ES384</td>
	<td>-35</td>		<td align="center" colspan="1" rowspan="1">-35</td>
	<td>SHA-384</td>		<td align="left" colspan="1" rowspan="1">SHA-384</td>
	<td>ECDSA w/ SHA-384</td>		<td align="left" colspan="1" rowspan="1">ECDSA w/ SHA-384</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>ES512</td>		<td align="left" colspan="1" rowspan="1">ES512</td>
	<td>-36</td>		<td align="center" colspan="1" rowspan="1">-36</td>
	<td>SHA-512</td>		<td align="left" colspan="1" rowspan="1">SHA-512</td>
	<td>ECDSA w/ SHA-512</td>		<td align="left" colspan="1" rowspan="1">ECDSA w/ SHA-512</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>This document defines ECDSA to work only with the curves P-256, P-384		<t indent="0" pn="section-2.1-5">This document defines ECDSA as working
	, and P-521. This document requires that the curves be encoded using the 'EC2'		only with the curves P-256,
	(two coordinate elliptic curve) key type. Implementations need to check that th		P-384, and P-521. This document requires that the curves be encoded
	e key type and curve are correct when creating and verifying a signature. Futur		using the "EC2" (two coordinate elliptic curve) key type.
	e documents may define it to work with other curves and points in the future. <		Implementations need to check that the key type and curve are correct
	/t>		when creating and verifying a signature. Future documents may define
	<t>In order to promote interoperability, it is suggested that SHA-256 be		it to work with other curves and key types in the future. </t>
	used only with curve P-256, SHA-384 be used only with curve P-384, and SHA-512		<t indent="0" pn="section-2.1-6">In order to promote interoperability, i
	be used with curve P-521. This is aligned with the recommendation in Section 4		t is suggested that SHA-256 be used only with curve P-256, SHA-384 be used only
	of <xref target="RFC5480"/>. </t>		with curve P-384, and SHA-512 be used only with curve P-521. This is aligned wi
	<t>		th the recommendation in <xref target="RFC5480" section="4" sectionFormat="of" f
			ormat="default" derivedLink="https://rfc-editor.org/rfc/rfc5480#section-4" deriv
			edContent="RFC5480"/>. </t>
			<t indent="0" pn="section-2.1-7">
	The signature algorithm results in a pair of integers (R, S).		The signature algorithm results in a pair of integers (R, S).
	These integers will be the same length as the length of the key used f or the signature process.		These integers will be the same length as the length of the key used f or the signature process.
	The signature is encoded by converting the integers into byte strings of the same length as the key size.		The signature is encoded by converting the integers into byte strings of the same length as the key size.
	The length is rounded up to the nearest byte and is left padded with z ero bits to get to the correct length.		The length is rounded up to the nearest byte and is left padded with z ero bits to get to the correct length.
	The two integers are then concatenated together to form a byte string that is the resulting signature.		The two integers are then concatenated together to form a byte string that is the resulting signature.
	</t>		</t>
	<t>		<t indent="0" pn="section-2.1-8">
	Using the function defined in <xref target="RFC8017"/>, the signature		Using the function defined in <xref target="RFC8017" format="default"
	is:		sectionFormat="of" derivedContent="RFC8017"/>, the signature is:
	</t>		</t>
	<t>		<t indent="0" pn="section-2.1-9">
	Signature = I2OSP(R, n) | I2OSP(S, n)		Signature = I2OSP(R, n) | I2OSP(S, n)
	</t>		</t>
	<t>		<t indent="0" pn="section-2.1-10">
	where n = ceiling(key_length / 8)		where n = ceiling(key_length / 8)
	</t>		</t>
	<t>When using a COSE key for this algorithm, the following checks are ma de:		<t indent="0" pn="section-2.1-11">When using a COSE key for this algorit hm, the following checks are made:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-2
	<ul>		.1-12">
			<li pn="section-2.1-12.1">The "kty" field <bcp14>MUST</bcp14> be prese
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		nt, and it <bcp14>MUST</bcp14> be "EC2".</li>
	</bcp14> be 'EC2'.</li>		<li pn="section-2.1-12.2">If the "alg" field is present, it <bcp14>MUS
			T</bcp14> match the ECDSA signature algorithm being used.</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the EC		<li pn="section-2.1-12.3">If the "key_ops" field is present, it <bcp14
	DSA signature algorithm being used.</li>		>MUST</bcp14> include "sign" when creating an ECDSA signature.</li>
			<li pn="section-2.1-12.4">If the "key_ops" field is present, it <bcp14
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		>MUST</bcp14> include "verify" when verifying an ECDSA signature.</li>
	'sign' when creating an ECDSA signature.</li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include
	'verify' when verifying an ECDSA signature.</li>
	</ul>		</ul>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-2
			.1.1">
	<name>Security Considerations for ECDSA</name>		<name slugifiedName="name-security-considerations-for">Security Consid
	<t>The security strength of the signature is no greater than the minim		erations for ECDSA</name>
	um of the security strength associated with the bit length of the key and the se		<t indent="0" pn="section-2.1.1-1">The security strength of the signat
	curity strength of the hash function. </t>		ure is no greater than the minimum of the security strength associated with the
	<t>		bit length of the key and the security strength of the hash function. </t>
	Note: Use of a deterministic signature technique is a good idea even		<t indent="0" pn="section-2.1.1-2">
	when good random number generation exists.		Note: Use of a deterministic signature technique is a good idea
	Doing so both reduces the possibility of having the same value of 'k		even when good random number generation exists.
	' in two signature operations and allows for reproducible signature values, whic		Doing so both reduces the possibility of having the same value of
	h helps testing.		"k" in two signature operations and allows for reproducible
	There have been recent attacks involving faulting the device in orde		signature values, which helps testing.
	r to extract the key.		There have been recent attacks involving faulting the device in
	This can be addressed by combining both randomness and determinism		order to extract the key.
	<xref target="I-D.mattsson-cfrg-det-sigs-with-noise"/>.		This can be addressed by combining both randomness and determinism
			<xref target="I-D.mattsson-cfrg-det-sigs-with-noise" format="default"
			sectionFormat="of" derivedContent="CFRG-DET-SIGS"/>.
	</t>		</t>
	<t>There are two substitution attacks that can theoretically be mounte d against the ECDSA signature algorithm.		<t indent="0" pn="section-2.1.1-3">There are two substitution attacks that can theoretically be mounted against the ECDSA signature algorithm.
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section
	<ul>		-2.1.1-4">
			<li pn="section-2.1.1-4.1">Changing the curve used to validate the s
	<li>Changing the curve used to validate the signature: If one change		ignature: If one
	s the curve used to validate the signature, then potentially one could have two		changes the curve used to validate the signature, then potentially
	messages with the same signature, each computed under a different curve. The on		one could have two messages with the same signature, each computed
	ly requirement on the new curve is that its order be the same as the old one and		under a different curve. The only requirements on the new curve are
	it be acceptable to the client. An example would be to change from using the c		that its order be the same as the old one and that it be acceptable t
	urve secp256r1 (aka P-256) to using secp256k1. (Both are 256-bit curves.) We cu		o
	rrently do not have any way to deal with this version of the attack except to re		the client. An example would be to change from using the curve
	strict the overall set of curves that can be used. </li>		secp256r1 (aka P-256) to using secp256k1. (Both are 256-bit
			curves.) We currently do not have any way to deal with this
	<li>Change the hash function used to validate the signature: If one		version of the attack except to restrict the overall set of curves
	either has two different hash functions of the same length or can truncate a has		that can be used. </li>
	h function, then one could potentially find collisions between the hash function		<li pn="section-2.1.1-4.2">Changing the hash function used to valida
	s rather than within a single hash function (for example, truncating SHA-512 to		te the signature: If
	256 bits might collide with a SHA-256 bit hash value). As the hash algorithm is		one either has two different hash functions of the same length or
	part of the signature algorithm identifier, this attack is mitigated by includin		can truncate a hash function, then one could potentially find
	g a signature algorithm identifier in the protected header bucket. </li>		collisions between the hash functions rather than within a single
			hash function. For example, truncating SHA-512 to 256 bits might
			collide with a SHA-256 bit hash value. As the hash algorithm is
			part of the signature algorithm identifier, this attack is
			mitigated by including a signature algorithm identifier in the
			protected-header bucket. </li>
	</ul>		</ul>
	</section>		</section>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-2.2
			">
	<name>Edwards-Curve Digital Signature Algorithms (EdDSAs)</name>		<name slugifiedName="name-edwards-curve-digital-signa">Edwards-Curve Dig
	<t><xref target="RFC8032"/> describes the elliptic curve signature schem		ital Signature Algorithm (EdDSA)</name>
	e Edwards-curve Digital Signature Algorithm (EdDSA). In that document, the sign		<t indent="0" pn="section-2.2-1"><xref target="RFC8032" format="default"
	ature algorithm is instantiated using parameters for edwards25519 and edwards448		sectionFormat="of" derivedContent="RFC8032"/> describes the elliptic curve sign
	curves. The document additionally describes two variants of the EdDSA algorith		ature
	m: Pure EdDSA, where no hash function is applied to the content before signing,		scheme Edwards-curve Digital Signature Algorithm (EdDSA). In that
	and HashEdDSA, where a hash function is applied to the content before signing an		document, the signature algorithm is instantiated using parameters for
	d the result of that hash function is signed. For EdDSA, the content to be sign		the edwards25519 and edwards448 curves. The document additionally
	ed (either the message or the pre-hash value) is processed twice inside of the s		describes two variants of the EdDSA algorithm: Pure EdDSA, where no
	ignature algorithm. For use with COSE, only the pure EdDSA version is used. Th		hash function is applied to the content before signing, and HashEdDSA,
	is is because it is not expected that extremely large contents are going to be n		where a hash function is applied to the content before signing and the
	eeded and, based on the arrangement of the message structure, the entire message		result of that hash function is signed. For EdDSA, the content to be
	is going to need to be held in memory in order to create or verify a signature.		signed (either the message or the prehash value) is processed twice
	This means that there does not appear to be a need to be able to do block upda		inside of the signature algorithm. For use with COSE, only the pure
	tes of the hash, followed by eliminating the message from memory. Applications		EdDSA version is used. This is because it is not expected that
	can provide the same features by defining the content of the message as a hash v		extremely large contents are going to be needed and, based on the
	alue and transporting the COSE object (with the hash value) and the content as s		arrangement of the message structure, the entire message is going to
	eparate items. </t>		need to be held in memory in order to create or verify a signature.
	<t>The algorithms defined in this document can be found in <xref target=		Therefore, there does not appear to be a need to be able to do
	"x-table-eddsa-algs"/>. A single signature algorithm is defined, which can be u		block updates of the hash, followed by eliminating the message from
	sed for multiple curves. </t>		memory. Applications can provide the same features by defining the
	<table anchor="x-table-eddsa-algs" align="center">		content of the message as a hash value and transporting the COSE
			object (with the hash value) and the content as separate items. </t>
	<name>EdDSA Algorithm Values</name>		<t indent="0" pn="section-2.2-2">The algorithm defined in this document
			can be found in <xref target="x-table-eddsa-algs" format="default" sectionFormat
			="of" derivedContent="Table 2"/>. A single signature algorithm is defined, whic
			h can be used for multiple curves. </t>
			<table anchor="x-table-eddsa-algs" align="center" pn="table-2">
			<name slugifiedName="name-eddsa-algorithm-value">EdDSA Algorithm Value
			</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>EdDSA</td>		<td align="left" colspan="1" rowspan="1">EdDSA</td>
	<td>-8</td>		<td align="center" colspan="1" rowspan="1">-8</td>
	<td>EdDSA</td>		<td align="left" colspan="1" rowspan="1">EdDSA</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t><xref target="RFC8032"/> describes the method of encoding the signatu		<t indent="0" pn="section-2.2-4"><xref target="RFC8032" format="default"
	re value. </t>		sectionFormat="of" derivedContent="RFC8032"/> describes the method of encoding
	<t>When using a COSE key for this algorithm, the following checks are ma		the signature value. </t>
	de:		<t indent="0" pn="section-2.2-5">When using a COSE key for this algorith
			m, the following checks are made:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-2
	<ul>		.2-6">
			<li pn="section-2.2-6.1">The "kty" field <bcp14>MUST</bcp14> be presen
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		t, and it <bcp14>MUST</bcp14> be "OKP" (Octet Key Pair). </li>
	</bcp14> be 'OKP' (Octet Key Pair). </li>		<li pn="section-2.2-6.2">The "crv" field <bcp14>MUST</bcp14> be presen
			t, and it <bcp14>MUST</bcp14> be a curve defined for this signature algorithm.</
	<li>The 'crv' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		li>
	</bcp14> be a curve defined for this signature algorithm.</li>		<li pn="section-2.2-6.3">If the "alg" field is present, it <bcp14>MUST
			</bcp14> match "EdDSA".</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match 'EdDSA		<li pn="section-2.2-6.4">If the "key_ops" field is present, it <bcp14>
	'.</li>		MUST</bcp14> include "sign" when creating an EdDSA signature.</li>
			<li pn="section-2.2-6.5">If the "key_ops" field is present, it <bcp14>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		MUST</bcp14> include "verify" when verifying an EdDSA signature.</li>
	'sign' when creating an EdDSA signature.</li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include
	'verify' when verifying an EdDSA signature.</li>
	</ul>		</ul>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-2
			.2.1">
	<name>Security Considerations for EdDSA</name>		<name slugifiedName="name-security-considerations-for-">Security Consi
	<t>How public values are computed is not the same when looking at EdDS		derations for EdDSA</name>
	A and Elliptic Curve Diffie-Hellman (ECDH); for this reason, the public key shou		<t indent="0" pn="section-2.2.1-1">Public values are computed differen
	ld not be used with the other algorithm. </t>		tly in EdDSA and Elliptic Curve
	<t>If batch signature verification is performed, a well-seeded cryptog		Diffie-Hellman (ECDH); for this reason, the public key from one should
	raphic random number generator is <bcp14>REQUIRED</bcp14> (<relref target="RFC80		not be
	32" section="8.2"/>). Signing and non-batch signature verification are determin		used with the other algorithm.</t>
	istic operations and do not need random numbers of any kind. </t>		<t indent="0" pn="section-2.2.1-2">If batch signature verification is
			performed, a well-seeded
			cryptographic random number generator is <bcp14>REQUIRED</bcp14>
			(<xref target="RFC8032" section="8.2" sectionFormat="of" format="defaul
			t" derivedLink="https://rfc-editor.org/rfc/rfc8032#section-8.2" derivedContent="
			RFC8032"/>). Signing and nonbatch
			signature verification are deterministic operations and do not need
			random numbers of any kind. </t>
	</section>		</section>
	</section>		</section>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-3">
			<name slugifiedName="name-message-authentication-code">Message Authenticat
	<name>Message Authentication Code (MAC) Algorithms</name>		ion Code (MAC) Algorithms</name>
	<t>		<t indent="0" pn="section-3-1">
	<relref section="&MacSection;" target="I-D.ietf-cose-rfc8152bis-struct"/		<xref section="8.2" target="RFC9052" sectionFormat="of" format="default"
	> contains a generic description of MAC algorithms.		derivedLink="https://rfc-editor.org/rfc/rfc9052#section-8.2" derivedContent="RFC
			9052"/> contains a generic description
			of MAC algorithms.
	This section defines the conventions for two MAC algorithms.		This section defines the conventions for two MAC algorithms.
	</t>		</t>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-3.1
			">
	<name>Hash-Based Message Authentication Codes (HMACs)</name>		<name slugifiedName="name-hash-based-message-authenti">Hash-Based Messag
	<t>HMAC <xref target="RFC2104"/> <xref target="RFC4231"/> was designed t		e Authentication Codes (HMACs)</name>
	o deal with length extension attacks. The algorithm was also designed to allow		<t indent="0" pn="section-3.1-1">HMAC <xref target="RFC2104" format="def
	for new hash algorithms to be directly plugged in without changes to the hash fu		ault" sectionFormat="of" derivedContent="RFC2104"/> <xref target="RFC4231" forma
	nction. The HMAC design process has been shown as solid since, while the securi		t="default" sectionFormat="of" derivedContent="RFC4231"/> was designed
	ty of hash algorithms such as MD5 has decreased over time; the security of HMAC		to deal with length extension attacks. The HMAC algorithm was also design
	combined with MD5 has not yet been shown to be compromised <xref target="RFC6151		ed to allow new hash functions to be
	"/>. </t>		directly plugged in without changes to the hash function. The HMAC design proc
	<t>The HMAC algorithm is parameterized by an inner and outer padding, a		ess has
	hash function (h), and an authentication tag value length. For this specificati		been shown to be solid; although the security of hash functions such
	on, the inner and outer padding are fixed to the values set in <xref target="RFC		as MD5 has decreased over time, the security of HMAC combined with MD5
	2104"/>. The length of the authentication tag corresponds to the difficulty of		has not yet been shown to be compromised <xref target="RFC6151" format="d
	producing a forgery. For use in constrained environments, we define one HMAC al		efault" sectionFormat="of" derivedContent="RFC6151"/>.
	gorithm that is truncated. There are currently no known issues with truncation;		</t>
	however, the security strength of the message tag is correspondingly reduced in		<t indent="0" pn="section-3.1-2">The HMAC algorithm is parameterized by
	strength. When truncating, the leftmost tag length bits are kept and transmitt		an inner and outer padding,
	ed. </t>		a hash function (h), and an authentication tag value length. For this
	<t>The algorithms defined in this document can be found in <xref target=		specification, the inner and outer padding are fixed to the values set
	"x-table-hmac"/>. </t>		in <xref target="RFC2104" format="default" sectionFormat="of" derivedCont
	<table anchor="x-table-hmac" align="center">		ent="RFC2104"/>. The length of the authentication tag
			corresponds to the difficulty of producing a forgery. For use in
	<name>HMAC Algorithm Values</name>		constrained environments, we define one HMAC algorithm that is
			truncated. There are currently no known issues with truncation;
			however, the security strength of the message tag is correspondingly
			reduced in strength. When truncating, the leftmost tag-length bits
			are kept and transmitted. </t>
			<t indent="0" pn="section-3.1-3">The algorithms defined in this document
			can be found in <xref target="x-table-hmac" format="default" sectionFormat="of"
			derivedContent="Table 3"/>. </t>
			<table anchor="x-table-hmac" align="center" pn="table-3">
			<name slugifiedName="name-hmac-algorithm-values">HMAC Algorithm Values
			</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Hash</th>		<th align="left" colspan="1" rowspan="1">Hash</th>
	<th>Tag Length</th>		<th align="center" colspan="1" rowspan="1">Tag Length</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>HMAC 256/64</td>		<td align="left" colspan="1" rowspan="1">HMAC 256/64</td>
	<td>4</td>		<td align="center" colspan="1" rowspan="1">4</td>
	<td>SHA-256</td>		<td align="left" colspan="1" rowspan="1">SHA-256</td>
	<td>64</td>		<td align="center" colspan="1" rowspan="1">64</td>
	<td>HMAC w/ SHA-256 truncated to 64 bits</td>		<td align="left" colspan="1" rowspan="1">HMAC w/ SHA-256 truncated
			to 64 bits</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>HMAC 256/256</td>		<td align="left" colspan="1" rowspan="1">HMAC 256/256</td>
	<td>5</td>		<td align="center" colspan="1" rowspan="1">5</td>
	<td>SHA-256</td>		<td align="left" colspan="1" rowspan="1">SHA-256</td>
	<td>256</td>		<td align="center" colspan="1" rowspan="1">256</td>
	<td>HMAC w/ SHA-256</td>		<td align="left" colspan="1" rowspan="1">HMAC w/ SHA-256</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>HMAC 384/384</td>		<td align="left" colspan="1" rowspan="1">HMAC 384/384</td>
	<td>6</td>		<td align="center" colspan="1" rowspan="1">6</td>
	<td>SHA-384</td>		<td align="left" colspan="1" rowspan="1">SHA-384</td>
	<td>384</td>		<td align="center" colspan="1" rowspan="1">384</td>
	<td>HMAC w/ SHA-384</td>		<td align="left" colspan="1" rowspan="1">HMAC w/ SHA-384</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>HMAC 512/512</td>		<td align="left" colspan="1" rowspan="1">HMAC 512/512</td>
	<td>7</td>		<td align="center" colspan="1" rowspan="1">7</td>
	<td>SHA-512</td>		<td align="left" colspan="1" rowspan="1">SHA-512</td>
	<td>512</td>		<td align="center" colspan="1" rowspan="1">512</td>
	<td>HMAC w/ SHA-512</td>		<td align="left" colspan="1" rowspan="1">HMAC w/ SHA-512</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>Some recipient algorithms transport the key, while others derive a ke		<t indent="0" pn="section-3.1-5">Some recipient algorithms transport the
	y from secret data. For those algorithms that transport the key (such as AES Ke		key, while others derive a key from secret data. For those algorithms that tra
	y Wrap), the size of the HMAC key <bcp14>SHOULD</bcp14> be the same size as the		nsport the key (such as AES Key Wrap), the size of the HMAC key <bcp14>SHOULD</b
	output of the underlying hash function. For those algorithms that derive the k		cp14> be the same size as the output of the underlying hash function. For thos
	ey (such as ECDH), the derived key <bcp14>MUST</bcp14> be the same size as the u		e algorithms that derive the key (such as ECDH), the derived key <bcp14>MUST</bc
	nderlying hash function. </t>		p14> be the same size as the output of the underlying hash function. </t>
	<t>When using a COSE key for this algorithm, the following checks are ma		<t indent="0" pn="section-3.1-6">When using a COSE key for this algorith
	de:		m, the following checks are made:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-3
	<ul>		.1-7">
			<li pn="section-3.1-7.1">The "kty" field <bcp14>MUST</bcp14> be presen
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		t, and it <bcp14>MUST</bcp14> be "Symmetric".</li>
	</bcp14> be 'Symmetric'.</li>		<li pn="section-3.1-7.2">If the "alg" field is present, it <bcp14>MUST
			</bcp14> match the HMAC algorithm being used.</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the HM		<li pn="section-3.1-7.3">If the "key_ops" field is present, it <bcp14>
	AC algorithm being used.</li>		MUST</bcp14> include "MAC create" when creating an HMAC authentication tag.</li>
			<li pn="section-3.1-7.4">If the "key_ops" field is present, it <bcp14>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		MUST</bcp14> include "MAC verify" when verifying an HMAC authentication tag.</li
	'MAC create' when creating an HMAC authentication tag.</li>		>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include
	'MAC verify' when verifying an HMAC authentication tag.</li>
	</ul>		</ul>
	<t>Implementations creating and validating MAC values <bcp14>MUST</bcp14		<t indent="0" pn="section-3.1-8">Implementations creating and validating
	> validate that the key type, key length, and algorithm are correct and appropri		MAC values <bcp14>MUST</bcp14> validate that the key type, key length, and algo
	ate for the entities involved. </t>		rithm are correct and appropriate for the entities involved. </t>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-3
			.1.1">
	<name>Security Considerations for HMAC</name>		<name slugifiedName="name-security-considerations-for-h">Security Cons
	<t>HMAC has proved to be resistant to attack even when used with weake		iderations for HMAC</name>
	ned hash algorithms. The current best known attack is to brute force the key.		<t indent="0" pn="section-3.1.1-1">HMAC has proved to be resistant to
	This means that key size is going to be directly related to the security of an H		attack even when used with weakened hash algorithms. The current best known att
	MAC operation. </t>		ack is to brute force the key. This means that key size is going to be directly
			related to the security of an HMAC operation. </t>
	</section>		</section>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-3.2
			">
	<name>AES Message Authentication Code (AES-CBC-MAC)</name>		<name slugifiedName="name-aes-message-authentication-">AES Message Authe
	<t>AES-CBC-MAC is defined in <xref target="MAC"/>. (Note that this is n		ntication Code (AES-CBC-MAC)</name>
	ot the same algorithm as AES Cipher-Based Message Authentication Code (AES-CMAC)		<t indent="0" pn="section-3.2-1">AES-CBC-MAC is the instantiation of the
	<xref target="RFC4493"/>.) </t>		CBC-MAC construction (defined in <xref target="MAC" format="default" sectionFor
	<t>AES-CBC-MAC is parameterized by the key length, the authentication ta		mat="of" derivedContent="MAC"/>) using AES as the block cipher. For brevity, we
	g length, and the Initialization Vector (IV) used. For all of these algorithms,		also use "AES-MAC"
	the IV is fixed to all zeros. We provide an array of algorithms for various ke		to refer to AES-CBC-MAC. (Note that this is
	y lengths and tag lengths. The algorithms defined in this document are found in		not the same algorithm as AES Cipher-Based Message Authentication Code
	<xref target="x-table-aes-mac"/>. </t>		(AES-CMAC) <xref target="RFC4493" format="default" sectionFormat="of" der
	<table anchor="x-table-aes-mac" align="center">		ivedContent="RFC4493"/>.) </t>
			<t indent="0" pn="section-3.2-2">AES-CBC-MAC is parameterized by the key
	<name>AES-MAC Algorithm Values</name>		length, the
			authentication tag length, and the Initialization Vector (IV) used.
			For all of these algorithms, the IV is fixed to all zeros. We provide
			an array of algorithms for various key and tag lengths. The
			algorithms defined in this document are found in <xref target="x-table-ae
			s-mac" format="default" sectionFormat="of" derivedContent="Table 4"/>. </t>
			<table anchor="x-table-aes-mac" align="center" pn="table-4">
			<name slugifiedName="name-aes-mac-algorithm-values">AES-MAC Algorithm
			Values</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Key Length</th>		<th align="center" colspan="1" rowspan="1">Key Length</th>
	<th>Tag Length</th>		<th align="center" colspan="1" rowspan="1">Tag Length</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>AES-MAC 128/64</td>		<td align="left" colspan="1" rowspan="1">AES-MAC 128/64</td>
	<td>14</td>		<td align="center" colspan="1" rowspan="1">14</td>
	<td>128</td>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>64</td>		<td align="center" colspan="1" rowspan="1">64</td>
	<td>AES-MAC 128-bit key, 64-bit tag</td>		<td align="left" colspan="1" rowspan="1">AES-MAC 128-bit key, 64-b
			it tag</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-MAC 256/64</td>		<td align="left" colspan="1" rowspan="1">AES-MAC 256/64</td>
	<td>15</td>		<td align="center" colspan="1" rowspan="1">15</td>
	<td>256</td>		<td align="center" colspan="1" rowspan="1">256</td>
	<td>64</td>		<td align="center" colspan="1" rowspan="1">64</td>
	<td>AES-MAC 256-bit key, 64-bit tag</td>		<td align="left" colspan="1" rowspan="1">AES-MAC 256-bit key, 64-b
			it tag</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-MAC 128/128</td>		<td align="left" colspan="1" rowspan="1">AES-MAC 128/128</td>
	<td>25</td>		<td align="center" colspan="1" rowspan="1">25</td>
	<td>128</td>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>128</td>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>AES-MAC 128-bit key, 128-bit tag</td>		<td align="left" colspan="1" rowspan="1">AES-MAC 128-bit key, 128-
			bit tag</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-MAC 256/128</td>		<td align="left" colspan="1" rowspan="1">AES-MAC 256/128</td>
	<td>26</td>		<td align="center" colspan="1" rowspan="1">26</td>
	<td>256</td>		<td align="center" colspan="1" rowspan="1">256</td>
	<td>128</td>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>AES-MAC 256-bit key, 128-bit tag</td>		<td align="left" colspan="1" rowspan="1">AES-MAC 256-bit key, 128-
			bit tag</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>Keys may be obtained either from a key structure or from a recipient		<t indent="0" pn="section-3.2-4">Keys may be obtained from either a key
	structure. Implementations creating and validating MAC values <bcp14>MUST</bcp1		structure or a
	4> validate that the key type, key length, and algorithm are correct and appropr		recipient structure. Implementations creating and validating MAC
	iate for the entities involved. </t>		values <bcp14>MUST</bcp14> validate that the key type, key length, and
	<t>When using a COSE key for this algorithm, the following checks are ma		algorithm are correct and appropriate for the entities involved. </t>
	de:		<t indent="0" pn="section-3.2-5">When using a COSE key for this algorith
			m, the following checks are made:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-3
	<ul>		.2-6">
			<li pn="section-3.2-6.1">The "kty" field <bcp14>MUST</bcp14> be presen
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		t, and it <bcp14>MUST</bcp14> be "Symmetric".</li>
	</bcp14> be 'Symmetric'.</li>		<li pn="section-3.2-6.2">If the "alg" field is present, it <bcp14>MUST
			</bcp14> match the AES-MAC algorithm being used.</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the AE		<li pn="section-3.2-6.3">If the "key_ops" field is present, it <bcp14>
	S-MAC algorithm being used.</li>		MUST</bcp14> include "MAC create" when creating an AES-MAC authentication tag.</
			li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		<li pn="section-3.2-6.4">If the "key_ops" field is present, it <bcp14>
	'MAC create' when creating an AES-MAC authentication tag.</li>		MUST</bcp14> include "MAC verify" when verifying an AES-MAC authentication tag.<
			/li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include
	'MAC verify' when verifying an AES-MAC authentication tag.</li>
	</ul>		</ul>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-3
			.2.1">
	<name>Security Considerations AES-CBC_MAC </name>		<name slugifiedName="name-security-considerations-for-a">Security Cons
	<t>A number of attacks exist against Cipher Block Chaining Message Aut		iderations for AES-CBC-MAC </name>
	hentication Code (CBC-MAC) that need to be considered.		<t indent="0" pn="section-3.2.1-1">A number of attacks exist against C
			ipher Block Chaining Message Authentication Code (CBC-MAC) that need to be consi
			dered.
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section
	<ul>		-3.2.1-2">
			<li pn="section-3.2.1-2.1">A single key must only be used for messag
	<li>A single key must only be used for messages of a fixed or known		es of a fixed or
	length. If this is not the case, an attacker will be able to generate a message		known length. If this is not the case, an attacker will be able
	with a valid tag given two message and tag pairs. This can be addressed by usi		to generate a message with a valid tag given two
	ng different keys for messages of different lengths.		message and tag pairs. This can be addressed by using different
			keys for
	The current structure mitigates this problem, as a specific encoding structure		messages of different lengths. The current structure mitigates
	that includes lengths is built and signed. (CMAC also addresses this issue.) </		this problem, as a specific encoding structure that includes
	li>		lengths is built and signed. (CMAC also addresses this issue.)
			</li>
	<li>In cipher Block Chaining (CBC) mode, if the same key is used for		<li pn="section-3.2.1-2.2">In Cipher Block Chaining (CBC) mode, if t
	both encryption and authentication operations, an attacker can produce messages		he same key is used
	with a valid authentication code. </li>		for both encryption and authentication operations, an attacker can
			produce messages with a valid authentication code. </li>
	<li>If the IV can be modified, then messages can be forged. This is		<li pn="section-3.2.1-2.3">If the IV can be modified, then messages
	addressed by fixing the IV to all zeros. </li>		can be forged. This is addressed by fixing the IV to all zeros. </li>
	</ul>		</ul>
	</section>		</section>
	</section>		</section>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-4">
			<name slugifiedName="name-content-encryption-algorith">Content Encryption
			Algorithms</name>
			<t indent="0" pn="section-4-1">
	<name>Content Encryption Algorithms</name>		<xref section="8.3" target="RFC9052" sectionFormat="of" format="default"
	<t>		derivedLink="https://rfc-editor.org/rfc/rfc9052#section-8.3" derivedContent="RF
	<relref section="&ContentSection;" target="I-D.ietf-cose-rfc8152bis-stru		C9052"/> contains a generic description
	ct"/> contains a generic description of Content Encryption algorithms.		of content encryption algorithms.
	This document defines the identifier and usages for three content encryp		This document defines the identifier and usages for three
	tion algorithms.		content encryption algorithms.
	</t>		</t>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-4.1
			">
	<name>AES GCM</name>		<name slugifiedName="name-aes-gcm">AES-GCM</name>
	<t>The Galois/Counter Mode (GCM) mode is a generic AEAD block cipher mod		<t indent="0" pn="section-4.1-1">The Galois/Counter Mode (GCM) mode is a
	e defined in <xref target="AES-GCM"/>. The GCM mode is combined with the AES bl		generic AEAD block cipher
	ock encryption algorithm to define an AEAD cipher. </t>		mode defined in <xref target="AES-GCM" format="default" sectionFormat="of
	<t>The GCM mode is parameterized by the size of the authentication tag a		" derivedContent="AES-GCM"/>. The GCM mode is combined
	nd the size of the nonce. This document fixes the size of the nonce at 96 bits.		with the AES block encryption algorithm to define an AEAD cipher.
	The size of the authentication tag is limited to a small set of values. For t		</t>
	his document however, the size of the authentication tag is fixed at 128 bits.		<t indent="0" pn="section-4.1-2">The GCM mode is parameterized by the si
	</t>		ze of the authentication tag
	<t>The set of algorithms defined in this document are in <xref target="x		and the size of the nonce. This document fixes the size of the nonce
	-table-AES-GCM"/>. </t>		at 96 bits. The size of the authentication tag is limited to a small
	<table anchor="x-table-AES-GCM" align="center">		set of values. For this document, however, the size of the
			authentication tag is fixed at 128 bits. </t>
	<name>Algorithm Value for AES-GCM</name>		<t indent="0" pn="section-4.1-3">The set of algorithms defined in this d
			ocument is in <xref target="x-table-AES-GCM" format="default" sectionFormat="of"
			derivedContent="Table 5"/>. </t>
			<table anchor="x-table-AES-GCM" align="center" pn="table-5">
			<name slugifiedName="name-algorithm-values-for-aes-gc">Algorithm Value
			s for AES-GCM</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>A128GCM</td>		<td align="left" colspan="1" rowspan="1">A128GCM</td>
	<td>1</td>		<td align="center" colspan="1" rowspan="1">1</td>
	<td>AES-GCM mode w/ 128-bit key, 128-bit tag</td>		<td align="left" colspan="1" rowspan="1">AES-GCM mode w/ 128-bit k
			ey, 128-bit tag</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>A192GCM</td>		<td align="left" colspan="1" rowspan="1">A192GCM</td>
	<td>2</td>		<td align="center" colspan="1" rowspan="1">2</td>
	<td>AES-GCM mode w/ 192-bit key, 128-bit tag</td>		<td align="left" colspan="1" rowspan="1">AES-GCM mode w/ 192-bit k
			ey, 128-bit tag</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>A256GCM</td>		<td align="left" colspan="1" rowspan="1">A256GCM</td>
	<td>3</td>		<td align="center" colspan="1" rowspan="1">3</td>
	<td>AES-GCM mode w/ 256-bit key, 128-bit tag</td>		<td align="left" colspan="1" rowspan="1">AES-GCM mode w/ 256-bit k
			ey, 128-bit tag</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>Keys may be obtained either from a key structure or from a recipient		<t indent="0" pn="section-4.1-5">Keys may be obtained from either a key
	structure. Implementations encrypting and decrypting <bcp14>MUST</bcp14> valida		structure or a recipient
	te that the key type, key length, and algorithm are correct and appropriate for		structure. Implementations that are encrypting or decrypting
	the entities involved. </t>		<bcp14>MUST</bcp14> validate that the key type, key length, and
	<t>When using a COSE key for this algorithm, the following checks are ma		algorithm are correct and appropriate for the entities involved. </t>
	de:		<t indent="0" pn="section-4.1-6">When using a COSE key for this algorith
			m, the following checks are made:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4
	<ul>		.1-7">
			<li pn="section-4.1-7.1">The "kty" field <bcp14>MUST</bcp14> be presen
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		t, and it <bcp14>MUST</bcp14> be "Symmetric".</li>
	</bcp14> be 'Symmetric'.</li>		<li pn="section-4.1-7.2">If the "alg" field is present, it <bcp14>MUST
			</bcp14> match the AES-GCM algorithm being used.</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the AE		<li pn="section-4.1-7.3">If the "key_ops" field is present, it <bcp14>
	S-GCM algorithm being used.</li>		MUST</bcp14> include "encrypt" or "wrap key" when encrypting.</li>
			<li pn="section-4.1-7.4">If the "key_ops" field is present, it <bcp14>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		MUST</bcp14> include "decrypt" or "unwrap key" when decrypting.</li>
	'encrypt' or 'wrap key' when encrypting.</li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include
	'decrypt' or 'unwrap key' when decrypting.</li>
	</ul>		</ul>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-4
			.1.1">
	<name>Security Considerations for AES-GCM</name>		<name slugifiedName="name-security-considerations-for-ae">Security Con
	<t>When using AES-GCM, the following restrictions <bcp14>MUST</bcp14>		siderations for AES-GCM</name>
	be enforced:		<t indent="0" pn="section-4.1.1-1">When using AES-GCM, the following r
			estrictions <bcp14>MUST</bcp14> be enforced:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section
	<ul>		-4.1.1-2">
			<li pn="section-4.1.1-2.1">The key and nonce pair <bcp14>MUST</bcp14
	<li>The key and nonce pair <bcp14>MUST</bcp14> be unique for every m		> be unique for every
	essage encrypted. </li>		message encrypted. </li>
			<li pn="section-4.1.1-2.2">The total number of messages encrypted fo
	<li>The total number of messages encrypted for a single key <bcp14>M		r a single key
	UST NOT</bcp14> exceed 2^32 <xref target="SP800-38d"/>. An explicit check is re		<bcp14>MUST NOT</bcp14> exceed 2<sup>32</sup> <xref target="SP800-38D
	quired only in environments where it is expected that it might be exceeded. </l		" format="default" sectionFormat="of" derivedContent="SP800-38D"/>.
	i>		An explicit check is required only in environments where it is expect
	<li>		ed that this limit might be exceeded. </li>
	A more recent analysis in <xref target="ROBUST"/> indicates that t		<li pn="section-4.1.1-2.3">
	he the number of failed decryptions needs to be taken into account as part deter		<xref target="RFC8446" format="default" sectionFormat="of" derived
	mining when a key roll-over is to be done.		Content="RFC8446"/> contains an analysis on the
	Following the recommendation of for DTLS, the number of failed mes		use of AES-CGM for its environment.
	sage decryptions should be limited to 2^36.		Based on that recommendation, one should restrict the number of
			messages encrypted to 2<sup>24.5</sup>.</li>
			<li pn="section-4.1.1-2.4">
			A more recent analysis in <xref target="ROBUST" format="default" s
			ectionFormat="of" derivedContent="ROBUST"/> indicates that
			the number of failed decryptions needs to be taken into account
			as part of determining when a key rollover is to be done.
			Following the recommendation in DTLS (<xref target="RFC9147" secti
			on="4.5.3" sectionFormat="of" format="default" derivedLink="https://rfc-editor.o
			rg/rfc/rfc9147#section-4.5.3" derivedContent="RFC9147"/>), the number of
			failed message decryptions should be limited to 2<sup>36</sup>.
	</li>		</li>
	</ul>		</ul>
	<t>Consideration was given to supporting smaller tag values; the const		<t indent="0" pn="section-4.1.1-3">Consideration was given to supporti
	rained community would desire tag sizes in the 64-bit range. Doing so drasticall		ng smaller tag values; the
	y changes both the maximum messages size (generally not an issue) and the number		constrained community would desire tag sizes in the 64-bit
	of times that a key can be used. Given that Counter with CBC-MAC (CCM) is the		range. Such use drastically changes both the maximum message size
	usual mode for constrained environments, restricted modes are not supported. </		(generally not an issue) and the number of times that a key can be
	t>		used. Given that Counter with CBC-MAC (CCM) is the usual mode for
			constrained environments, restricted modes are not supported. </t>
	</section>		</section>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-4.2
			">
	<name>AES CCM</name>		<name slugifiedName="name-aes-ccm">AES-CCM</name>
	<t>CCM is a generic authentication encryption block cipher mode defined		<t indent="0" pn="section-4.2-1">CCM is a generic authentication encrypt
	in <xref target="RFC3610"/>. The CCM mode is combined with the AES block encryp		ion block cipher mode
	tion algorithm to define a commonly used content encryption algorithm used in co		defined in <xref target="RFC3610" format="default" sectionFormat="of" der
	nstrained devices. </t>		ivedContent="RFC3610"/>. The CCM mode is combined with
	<t>The CCM mode has two parameter choices. The first choice is M, the s		the AES block encryption algorithm to define an AEAD cipher that is
	ize of the authentication field. The choice of the value for M involves a trade		commonly used in constrained devices. </t>
	-off between message growth (from the tag) and the probability that an attacker		<t indent="0" pn="section-4.2-2">The CCM mode has two parameter choices.
	can undetectably modify a message. The second choice is L, the size of the leng		The first choice is M, the
	th field. This value requires a trade-off between the maximum message size and		size of the authentication field. The choice of the value for M
	the size of the Nonce. </t>		involves a trade-off between message growth (from the tag) and the
	<t>It is unfortunate that the specification for CCM specified L and M as		probability that an attacker can undetectably modify a message. The
	a count of bytes rather than a count of bits. This leads to possible misunders		second choice is L, the size of the length field. This value requires
	tandings where AES-CCM-8 is frequently used to refer to a version of CCM mode wh		a trade-off between the maximum message size and the size of the
	ere the size of the authentication is 64 bits and not 8 bits. These values have		nonce. </t>
	traditionally been specified as bit counts rather than byte counts. This docum		<t indent="0" pn="section-4.2-3">It is unfortunate that the specificatio
	ent will follow the convention of using bit counts so that it is easier to compa		n for CCM specified L and M as a count of bytes rather than a count of bits. Th
	re the different algorithms presented in this document. </t>		is leads to possible misunderstandings where AES-CCM-8 is frequently used to ref
	<t>We define a matrix of algorithms in this document over the values of		er to a version of CCM mode where the size of the authentication is 64 bits and
	L and M. Constrained devices are usually operating in situations where they use		not 8 bits. In most cryptographic algorithm specifications, these values have t
	short messages and want to avoid doing recipient-specific cryptographic operati		raditionally been specified as bit counts rather than byte counts. This documen
	ons. This favors smaller values of both L and M. Less-constrained devices will		t will follow the convention of using bit counts so that it is easier to compare
	want to be able to use larger messages and are more willing to generate new key		the different algorithms presented in this document. </t>
	s for every operation. This favors larger values of L and M. </t>		<t indent="0" pn="section-4.2-4">We define a matrix of algorithms in thi
	<t>The following values are used for L:		s document over the values of L and M. Constrained devices are usually operatin
			g in situations where they use short messages and want to avoid doing recipient-
			specific cryptographic operations. This favors smaller values of both L and M.
			Less-constrained devices will want to be able to use larger messages and are mo
			re willing to generate new keys for every operation. This favors larger values
			of L and M. </t>
			<t indent="0" pn="section-4.2-5">The following values are used for L:
	</t>		</t>
			<dl newline="false" indent="3" spacing="normal" pn="section-4.2-6">
	<dl newline="false">		<dt pn="section-4.2-6.1">16 bits (2):</dt>
	<dt>16 bits (2):</dt>		<dd pn="section-4.2-6.2">This limits messages to 2<sup>16</sup> bytes
			(64 KiB) in length.
	<dd>This limits messages to 2^16 bytes (64 KiB) in length. This is su		This is sufficiently long for messages in the constrained world.
	fficiently long for messages in the constrained world. The nonce length is 13 b		The nonce length is 13 bytes allowing for 2<sup>104</sup> possible valu
	ytes allowing for 2^104 possible values of the nonce without repeating. </dd>		es of
	<dt>64 bits (8):</dt>		the nonce without repeating. </dd>
			<dt pn="section-4.2-6.3">64 bits (8):</dt>
	<dd>This limits messages to 2^64 bytes in length. The nonce length is		<dd pn="section-4.2-6.4">This limits messages to 2<sup>64</sup> bytes
	7 bytes allowing for 2^56 possible values of the nonce without repeating. </dd		in length. The
	>		nonce length is 7 bytes, allowing for 2<sup>56</sup> possible values of
			the nonce without repeating. </dd>
	</dl>		</dl>
	<t>The following values are used for M:		<t indent="0" pn="section-4.2-7">The following values are used for M:
	</t>		</t>
			<dl newline="false" indent="3" spacing="normal" pn="section-4.2-8">
	<dl newline="false">		<dt pn="section-4.2-8.1">64 bits (8):</dt>
	<dt>64 bits (8):</dt>		<dd pn="section-4.2-8.2">This produces a 64-bit authentication tag. T
			his implies that
	<dd>This produces a 64-bit authentication tag. This implies that ther		there is a 1 in 2<sup>64</sup> chance that a modified message will
	e is a 1 in 2^64 chance that a modified message will authenticate. </dd>		authenticate.</dd>
	<dt>128 bits (16):</dt>		<dt pn="section-4.2-8.3">128 bits (16):</dt>
			<dd pn="section-4.2-8.4">This produces a 128-bit authentication tag.
	<dd>This produces a 128-bit authentication tag. This implies that the		This implies that
	re is a 1 in 2^128 chance that a modified message will authenticate. </dd>		there is a 1 in 2<sup>128</sup> chance that a modified message will
			authenticate.</dd>
	</dl>		</dl>
	<table anchor="x-table-AES-CCM" align="center">		<table anchor="x-table-AES-CCM" align="center" pn="table-6">
			<name slugifiedName="name-algorithm-values-for-aes-cc">Algorithm Value
	<name>Algorithm Values for AES-CCM</name>		s for AES-CCM</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>L</th>		<th align="left" colspan="1" rowspan="1">L</th>
	<th>M</th>		<th align="left" colspan="1" rowspan="1">M</th>
	<th>Key Length</th>		<th align="center" colspan="1" rowspan="1">Key Length</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>AES-CCM-16-64-128</td>		<td align="left" colspan="1" rowspan="1">AES-CCM-16-64-128</td>
	<td>10</td>		<td align="center" colspan="1" rowspan="1">10</td>
	<td>16</td>		<td align="left" colspan="1" rowspan="1">16</td>
	<td>64</td>		<td align="left" colspan="1" rowspan="1">64</td>
	<td>128</td>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>AES-CCM mode 128-bit key, 64-bit tag, 13-byte nonce</td>		<td align="left" colspan="1" rowspan="1">AES-CCM mode 128-bit key,
			64-bit tag, 13-byte nonce</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-CCM-16-64-256</td>		<td align="left" colspan="1" rowspan="1">AES-CCM-16-64-256</td>
	<td>11</td>		<td align="center" colspan="1" rowspan="1">11</td>
	<td>16</td>		<td align="left" colspan="1" rowspan="1">16</td>
	<td>64</td>		<td align="left" colspan="1" rowspan="1">64</td>
	<td>256</td>		<td align="center" colspan="1" rowspan="1">256</td>
	<td>AES-CCM mode 256-bit key, 64-bit tag, 13-byte nonce</td>		<td align="left" colspan="1" rowspan="1">AES-CCM mode 256-bit key,
			64-bit tag, 13-byte nonce</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-CCM-64-64-128</td>		<td align="left" colspan="1" rowspan="1">AES-CCM-64-64-128</td>
	<td>12</td>		<td align="center" colspan="1" rowspan="1">12</td>
	<td>64</td>		<td align="left" colspan="1" rowspan="1">64</td>
	<td>64</td>		<td align="left" colspan="1" rowspan="1">64</td>
	<td>128</td>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>AES-CCM mode 128-bit key, 64-bit tag, 7-byte nonce</td>		<td align="left" colspan="1" rowspan="1">AES-CCM mode 128-bit key,
			64-bit tag, 7-byte nonce</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-CCM-64-64-256</td>		<td align="left" colspan="1" rowspan="1">AES-CCM-64-64-256</td>
	<td>13</td>		<td align="center" colspan="1" rowspan="1">13</td>
	<td>64</td>		<td align="left" colspan="1" rowspan="1">64</td>
	<td>64</td>		<td align="left" colspan="1" rowspan="1">64</td>
	<td>256</td>		<td align="center" colspan="1" rowspan="1">256</td>
	<td>AES-CCM mode 256-bit key, 64-bit tag, 7-byte nonce</td>		<td align="left" colspan="1" rowspan="1">AES-CCM mode 256-bit key,
			64-bit tag, 7-byte nonce</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-CCM-16-128-128</td>		<td align="left" colspan="1" rowspan="1">AES-CCM-16-128-128</td>
	<td>30</td>		<td align="center" colspan="1" rowspan="1">30</td>
	<td>16</td>		<td align="left" colspan="1" rowspan="1">16</td>
	<td>128</td>		<td align="left" colspan="1" rowspan="1">128</td>
	<td>128</td>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>AES-CCM mode 128-bit key, 128-bit tag, 13-byte nonce</td>		<td align="left" colspan="1" rowspan="1">AES-CCM mode 128-bit key,
			128-bit tag, 13-byte nonce</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-CCM-16-128-256</td>		<td align="left" colspan="1" rowspan="1">AES-CCM-16-128-256</td>
	<td>31</td>		<td align="center" colspan="1" rowspan="1">31</td>
	<td>16</td>		<td align="left" colspan="1" rowspan="1">16</td>
	<td>128</td>		<td align="left" colspan="1" rowspan="1">128</td>
	<td>256</td>		<td align="center" colspan="1" rowspan="1">256</td>
	<td>AES-CCM mode 256-bit key, 128-bit tag, 13-byte nonce</td>		<td align="left" colspan="1" rowspan="1">AES-CCM mode 256-bit key,
			128-bit tag, 13-byte nonce</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-CCM-64-128-128</td>		<td align="left" colspan="1" rowspan="1">AES-CCM-64-128-128</td>
	<td>32</td>		<td align="center" colspan="1" rowspan="1">32</td>
	<td>64</td>		<td align="left" colspan="1" rowspan="1">64</td>
	<td>128</td>		<td align="left" colspan="1" rowspan="1">128</td>
	<td>128</td>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>AES-CCM mode 128-bit key, 128-bit tag, 7-byte nonce</td>		<td align="left" colspan="1" rowspan="1">AES-CCM mode 128-bit key,
			128-bit tag, 7-byte nonce</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>AES-CCM-64-128-256</td>		<td align="left" colspan="1" rowspan="1">AES-CCM-64-128-256</td>
	<td>33</td>		<td align="center" colspan="1" rowspan="1">33</td>
	<td>64</td>		<td align="left" colspan="1" rowspan="1">64</td>
	<td>128</td>		<td align="left" colspan="1" rowspan="1">128</td>
	<td>256</td>		<td align="center" colspan="1" rowspan="1">256</td>
	<td>AES-CCM mode 256-bit key, 128-bit tag, 7-byte nonce</td>		<td align="left" colspan="1" rowspan="1">AES-CCM mode 256-bit key,
			128-bit tag, 7-byte nonce</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>Keys may be obtained either from a key structure or from a recipient		<t indent="0" pn="section-4.2-10">Keys may be obtained from either a key
	structure. Implementations encrypting and decrypting <bcp14>MUST</bcp14> valida		structure or a recipient
	te that the key type, key length, and algorithm are correct and appropriate for		structure. Implementations that are encrypting or decrypting
	the entities involved. </t>		<bcp14>MUST</bcp14> validate that the key type, key length, and
	<t>When using a COSE key for this algorithm, the following checks are ma		algorithm are correct and appropriate for the entities involved. </t>
	de:		<t indent="0" pn="section-4.2-11">When using a COSE key for this algorit
			hm, the following checks are made:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4
	<ul>		.2-12">
			<li pn="section-4.2-12.1">The "kty" field <bcp14>MUST</bcp14> be prese
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		nt, and it <bcp14>MUST</bcp14> be "Symmetric".</li>
	</bcp14> be 'Symmetric'.</li>		<li pn="section-4.2-12.2">If the "alg" field is present, it <bcp14>MUS
			T</bcp14> match the AES-CCM algorithm being used.</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the AE		<li pn="section-4.2-12.3">If the "key_ops" field is present, it <bcp14
	S-CCM algorithm being used.</li>		>MUST</bcp14> include "encrypt" or "wrap key" when encrypting.</li>
			<li pn="section-4.2-12.4">If the "key_ops" field is present, it <bcp14
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		>MUST</bcp14> include "decrypt" or "unwrap key" when decrypting.</li>
	'encrypt' or 'wrap key' when encrypting.</li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include
	'decrypt' or 'unwrap key' when decrypting.</li>
	</ul>		</ul>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-4
			.2.1">
	<name>Security Considerations for AES-CCM</name>		<name slugifiedName="name-security-considerations-for-aes">Security Co
	<t>When using AES-CCM, the following restrictions <bcp14>MUST</bcp14>		nsiderations for AES-CCM</name>
	be enforced:		<t indent="0" pn="section-4.2.1-1">When using AES-CCM, the following r
			estrictions <bcp14>MUST</bcp14> be enforced:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section
	<ul>		-4.2.1-2">
			<li pn="section-4.2.1-2.1">The key and nonce pair <bcp14>MUST</bcp14
	<li>The key and nonce pair <bcp14>MUST</bcp14> be unique for every m		> be unique for every message encrypted. Note that the value of L influences the
	essage encrypted. Note that the value of L influences the number of unique nonce		number of unique nonces. </li>
	s. </li>		<li pn="section-4.2.1-2.2">The total number of times the AES block c
			ipher is used
	<li>The total number of times the AES block cipher is used <bcp14>MU		<bcp14>MUST NOT</bcp14> exceed 2<sup>61</sup> operations. This
	ST NOT</bcp14> exceed 2^61 operations. This limitation is the sum of times the		limit is the sum of times the block cipher is used in
	block cipher is used in computing the MAC value and in performing stream encrypt		computing the MAC value and performing stream encryption
	ion operations. An explicit check is required only in environments where it is		operations. An explicit check is required only in environments
	expected that it might be exceeded. </li>		where it is expected that this limit might be exceeded. </li>
	<li>		<li pn="section-4.2.1-2.3">
	<xref target="I-D.ietf-quic-tls"/> contains an analysis on the use		<xref target="RFC9147" format="default" sectionFormat="of" derived
	of AES-CCM in that environment.		Content="RFC9147"/> contains an analysis on the
	Based on that reommendation, one should restrict the number of mes		use of AES-CCM for its environment.
	sages encrypted to 2^23.		Based on that recommendation, one should restrict the number of
	If one is using the 64-bit tag, then the limits are signficantly s		messages encrypted to 2<sup>23</sup>.
	maller if one wants to keep the same integrity limits.
	A protocol recommending this needs to analysis what level of integ
	rity is acceptable for the smaller tag size.
	It may be that to keep the desired integrity one needs to re-key a
	s often as every 2^7 messages.
	</li>		</li>
	<li>		<li pn="section-4.2.1-2.4">
	In addition to the number of messages successfully decrypted, the		In addition to the number of messages successfully decrypted, the
	number of failed decryptions needs to be kept as well.		number of failed decryptions needs to be tracked as well.
	If the number of failed decryptions exceeds 2^23 then a rekeying o		Following the recommendation in DTLS (<xref target="RFC9147" secti
	peration should occur.		on="4.5.3" sectionFormat="of" format="default" derivedLink="https://rfc-editor.o
			rg/rfc/rfc9147#section-4.5.3" derivedContent="RFC9147"/>),
			the number of failed message decryptions should be limited to 2<sup>23.5</sup>.
			If one is using the 64-bit tag, then the limits are significantly
			smaller if one wants to keep the same integrity limits.
			A protocol recommending this needs to analyze what level of integr
			ity is acceptable for the smaller tag size.
			It may be that, to keep the desired level of integrity, one needs
			to rekey as often as every 2<sup>7</sup> messages.
	</li>		</li>
	</ul>		</ul>
	<t><xref target="RFC3610"/> additionally calls out one other considera		<t indent="0" pn="section-4.2.1-3"><xref target="RFC3610" format="defa
	tion of note. It is possible to do a pre-computation attack against the algorit		ult" sectionFormat="of" derivedContent="RFC3610"/> additionally calls out one ot
	hm in cases where portions of the plaintext are highly predictable. This reduc		her
	es the security of the key size by half. Ways to deal with this attack include		consideration of note. It is possible to do a precomputation
	adding a random portion to the nonce value and/or increasing the key size used.		attack against the algorithm in cases where portions of the
	Using a portion of the nonce for a random value will decrease the number of mes		plaintext are highly predictable. This reduces the security of the
	sages that a single key can be used for. Increasing the key size may require mo		key size by half. Ways to deal with this attack include adding a
	re resources in the constrained device. See Sections 5 and 10 of <xref target="		random portion to the nonce value and/or increasing the key size
	RFC3610"/> for more information. </t>		used. Using a portion of the nonce for a random value will decrease
			the number of messages that a single key can be used for.
			Increasing the key size may require more resources in the
			constrained device. See Sections <xref target="RFC3610" section="5" se
			ctionFormat="bare" format="default" derivedLink="https://rfc-editor.org/rfc/rfc3
			610#section-5" derivedContent="RFC3610"/> and <xref target="RFC3610" section="10
			" sectionFormat="bare" format="default" derivedLink="https://rfc-editor.org/rfc/
			rfc3610#section-10" derivedContent="RFC3610"/> of <xref target="RFC3610" format=
			"default" sectionFormat="of" derivedContent="RFC3610"/> for more
			information. </t>
	</section>		</section>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-4.3
			">
	<name>ChaCha20 and Poly1305</name>		<name slugifiedName="name-chacha20-and-poly1305">ChaCha20 and Poly1305</
	<t>ChaCha20 and Poly1305 combined together is an AEAD mode that is defin		name>
	ed in <xref target="RFC8439"/>. This is an algorithm defined to be a cipher tha		<t indent="0" pn="section-4.3-1">ChaCha20 and Poly1305 combined together
	t is not AES and thus would not suffer from any future weaknesses found in AES.		is an AEAD mode that is defined in <xref target="RFC8439" format="default" sect
	These cryptographic functions are designed to be fast in software-only implemen		ionFormat="of" derivedContent="RFC8439"/>. This is an algorithm defined using a
	tations. </t>		cipher that is not AES and thus would not suffer from any future weaknesses fou
	<t>The ChaCha20/Poly1305 AEAD construction defined in <xref target="RFC8		nd in AES. These cryptographic functions are designed to be fast in software-on
	439"/> has no parameterization. It takes a 256-bit key and a 96-bit nonce, as w		ly implementations. </t>
	ell as the plaintext and additional data as inputs and produces the ciphertext a		<t indent="0" pn="section-4.3-2">The ChaCha20/Poly1305 AEAD construction
	s an option. We define one algorithm identifier for this algorithm in <xref tar		defined in <xref target="RFC8439" format="default" sectionFormat="of" derivedCo
	get="x-table-CHACHA"/>. </t>		ntent="RFC8439"/> has no parameterization. It takes as inputs a
	<table anchor="x-table-CHACHA" align="center">		256-bit key and a 96-bit nonce, as well as the plaintext and
			additional data, and produces the ciphertext as an output. We define
	<name>Algorithm Value for ChaCha20/Poly1305</name>		one algorithm identifier for this algorithm in <xref target="x-table-CHAC
			HA" format="default" sectionFormat="of" derivedContent="Table 7"/>. </t>
			<table anchor="x-table-CHACHA" align="center" pn="table-7">
			<name slugifiedName="name-algorithm-value-for-chacha2">Algorithm Value
			for ChaCha20/Poly1305</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>ChaCha20/Poly1305</td>		<td align="left" colspan="1" rowspan="1">ChaCha20/Poly1305</td>
	<td>24</td>		<td align="center" colspan="1" rowspan="1">24</td>
	<td>ChaCha20/Poly1305 w/ 256-bit key, 128-bit tag</td>		<td align="left" colspan="1" rowspan="1">ChaCha20/Poly1305 w/ 256-
			bit key, 128-bit tag</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>Keys may be obtained either from a key structure or from a recipient		<t indent="0" pn="section-4.3-4">Keys may be obtained from either a key
	structure. Implementations encrypting and decrypting <bcp14>MUST</bcp14> valida		structure or a recipient
	te that the key type, key length, and algorithm are correct and appropriate for		structure. Implementations that are encrypting or decrypting
	the entities involved. </t>		<bcp14>MUST</bcp14> validate that the key type, key length, and
	<t>When using a COSE key for this algorithm, the following checks are ma		algorithm are correct and appropriate for the entities involved. </t>
	de:		<t indent="0" pn="section-4.3-5">When using a COSE key for this algorith
			m, the following checks are made:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4
	<ul>		.3-6">
			<li pn="section-4.3-6.1">The "kty" field <bcp14>MUST</bcp14> be presen
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		t, and it <bcp14>MUST</bcp14> be "Symmetric".</li>
	</bcp14> be 'Symmetric'.</li>		<li pn="section-4.3-6.2">If the "alg" field is present, it <bcp14>MUST
			</bcp14> match the ChaCha20/Poly1305 algorithm being used.</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the Ch		<li pn="section-4.3-6.3">If the "key_ops" field is present, it <bcp14>
	aCha20/Poly1305 algorithm being used.</li>		MUST</bcp14> include "encrypt" or "wrap key" when encrypting.</li>
			<li pn="section-4.3-6.4">If the "key_ops" field is present, it <bcp14>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		MUST</bcp14> include "decrypt" or "unwrap key" when decrypting.</li>
	'encrypt' or 'wrap key' when encrypting.</li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include
	'decrypt' or 'unwrap key' when decrypting.</li>
	</ul>		</ul>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-4
			.3.1">
	<name>Security Considerations for ChaCha20/Poly1305</name>		<name slugifiedName="name-security-considerations-for-c">Security Cons
	<t>The key and nonce values <bcp14>MUST</bcp14> be a unique pair for e		iderations for ChaCha20/Poly1305</name>
	very invocation of the algorithm. Nonce counters are considered to be an accept		<t indent="0" pn="section-4.3.1-1">The key and nonce values <bcp14>MUS
	able way of ensuring that they are unique. </t>		T</bcp14> be a unique pair for every invocation of the algorithm. Nonce counter
	<t>		s are considered to be an acceptable way of ensuring that they are unique. </t>
	A more recent analysis in <xref target="ROBUST"/> indicates that t		<t indent="0" pn="section-4.3.1-2">A more recent analysis in <xref tar
	he the number of failed decryptions needs to be taken into account as part deter		get="ROBUST" format="default" sectionFormat="of" derivedContent="ROBUST"/> indic
	mining when a key roll-over is to be done.		ates that
	Following the recommendation of for DTLS, the number of failed mes		the number of failed decryptions needs to be taken into account as
	sage decryptions should be limited to 2^36.		part of determining when a key rollover is to be done. Following the
			recommendation in DTLS (<xref target="RFC9147" section="4.5.3" sectionF
			ormat="of" format="default" derivedLink="https://rfc-editor.org/rfc/rfc9147#sect
			ion-4.5.3" derivedContent="RFC9147"/>), the number of failed message decryptions
			should be limited to 2<sup>36</sup>.
	</t>		</t>
	<t>		<t indent="0" pn="section-4.3.1-3">
	<xref target="I-D.ietf-quic-tls"/> recommends that no more than 2^		<xref target="RFC8446" format="default" sectionFormat="of" derived
	24.5 messages be encrypted under a single key.		Content="RFC8446"/> notes that the (64-bit) record sequence
			number would wrap before the safety limit is reached for ChaCha20/Poly1305.
			COSE implementations should not send more than 2<sup>64</sup> messages
			encrypted using a single ChaCha20/Poly1305 key.
	</t>		</t>
	</section>		</section>
	</section>		</section>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-5">
			<name slugifiedName="name-key-derivation-functions-kd">Key Derivation Func
	<name>Key Derivation Functions (KDFs)</name>		tions (KDFs)</name>
	<t>		<t indent="0" pn="section-5-1">
	<relref section="&KDFSection;" target="I-D.ietf-cose-rfc8152bis-struct"/		<xref section="8.4" target="RFC9052" sectionFormat="of" format="default"
	> contains a generic description of Key Derivation Functions.		derivedLink="https://rfc-editor.org/rfc/rfc9052#section-8.4" derivedContent="RF
			C9052"/> contains a generic description
			of key derivation functions.
	This document defines a single context structure and a single KDF.		This document defines a single context structure and a single KDF.
	These elements are used for all of the recipient algorithms defined in t		These elements are used for all of the recipient algorithms defined in
	his document that require a KDF process.		this document that require a KDF process.
	These algorithms are defined in Sections <xref target="direct-kdf" forma		These algorithms are defined in Sections <xref target="direct-kdf" forma
	t="counter"/>, <xref target="ECDH" format="counter"/>, and <xref target="ECDH-wr		t="counter" sectionFormat="of" derivedContent="6.1.2"/>, <xref target="ECDH" for
	ap" format="counter"/>.		mat="counter" sectionFormat="of" derivedContent="6.3.1"/>, and <xref target="ECD
			H-wrap" format="counter" sectionFormat="of" derivedContent="6.4.1"/>.
	</t>		</t>
	<section anchor="HKDF-section">		<section anchor="HKDF-section" numbered="true" removeInRFC="false" toc="in
			clude" pn="section-5.1">
	<name>HMAC-Based Extract-and-Expand Key Derivation Function (HKDF)</name		<name slugifiedName="name-hmac-based-extract-and-expa">HMAC-Based Extrac
	>		t-and-Expand Key Derivation Function (HKDF)</name>
	<t>The HKDF key derivation algorithm is defined in <xref target="RFC5869		<t indent="0" pn="section-5.1-1">The HKDF key derivation algorithm is de
	"/><xref target="HKDF"/>. </t>		fined in <xref target="RFC5869" format="default" sectionFormat="of" derivedConte
	<t>The HKDF algorithm takes these inputs:		nt="RFC5869"/> and <xref target="HKDF" format="default" sectionFormat="of" deriv
	</t>		edContent="HKDF"/>. </t>
			<t indent="0" pn="section-5.1-2">The HKDF algorithm takes these inputs:<
	<ul empty="true">		/t>
			<dl indent="3" newline="false" spacing="normal" pn="section-5.1-3">
	<li>secret -- a shared value that is secret. Secrets may be either pr		<dt pn="section-5.1-3.1">secret:</dt>
	eviously shared or derived from operations like a Diffie-Hellman (DH) key agreem		<dd pn="section-5.1-3.2"> A shared value that is secret. Secrets may
	ent. </li>		be
			either previously shared or derived from operations like a
	<li>salt -- an optional value that is used to change the generation pr		Diffie-Hellman (DH) key agreement. </dd>
	ocess. The salt value can be either public or private. If the salt is public a		<dt pn="section-5.1-3.3">salt:</dt>
	nd carried in the message, then the 'salt' algorithm header parameter defined in		<dd pn="section-5.1-3.4"> An optional value that is used to change the
	<xref target="HKDF_Alg_Params"/> is used. While <xref target="RFC5869"/> sugge		generation process. The salt value can be either public or private.
	sts that the length of the salt be the same as the length of the underlying hash		If the salt is public and carried in the message, then the "salt"
	value, any positive salt length will improve the security as different key valu		algorithm header parameter defined in <xref target="HKDF_Alg_Params" fo
	es will be generated. This parameter is protected by being included in the key		rmat="default" sectionFormat="of" derivedContent="Table 9"/> is used. While <xr
	computation and does not need to be separately authenticated. The salt value do		ef target="RFC5869" format="default" sectionFormat="of" derivedContent="RFC5869"
	es not need to be unique for every message sent. </li>		/>
			suggests that the length of the salt be the same as the length of
	<li>length -- the number of bytes of output that need to be generated.		the underlying hash value, any positive salt length will improve the
	</li>		security, as different key values will be generated. This parameter
			is protected by being included in the key computation and does not
	<li>context information -- Information that describes the context in w		need to be separately authenticated. The salt value does not need
	hich the resulting value will be used. Making this information specific to the		to be unique for every message sent. </dd>
	context in which the material is going to be used ensures that the resulting mat		<dt pn="section-5.1-3.5">length:</dt>
	erial will always be tied to that usage. The context structure defined in <xref		<dd pn="section-5.1-3.6">The number of bytes of output that need to be
	target="context"/> is used by the KDFs in this document. </li>		generated. </dd>
			<dt pn="section-5.1-3.7">context information:</dt>
	<li>PRF -- The underlying pseudorandom function to be used in the HKDF		<dd pn="section-5.1-3.8">Information that describes the
	algorithm. The PRF is encoded into the HKDF algorithm selection. </li>		context in which the resulting value will be used. Making this
	</ul>		information specific to the context in which the material is going
	<t>HKDF is defined to use HMAC as the underlying PRF. However, it is po		to be used ensures that the resulting material will always be tied
	ssible to use other functions in the same construct to provide a different KDF t		to that usage. The context structure defined in <xref target="context"
	hat is more appropriate in the constrained world. Specifically, one can use AES		format="default" sectionFormat="of" derivedContent="Section 5.2"/> is used by t
	-CBC-MAC as the PRF for the expand step, but not for the extract step. When usi		he KDFs in this document. </dd>
	ng a good random shared secret of the correct length, the extract step can be sk		<dt pn="section-5.1-3.9">PRF:</dt>
	ipped. For the AES algorithm versions, the extract step is always skipped. </t		<dd pn="section-5.1-3.10"> The underlying pseudorandom function to be
	>		used in
	<t>The extract step cannot be skipped if the secret is not uniformly ran		the HKDF algorithm. The PRF is encoded into the HKDF algorithm
	dom, for example, if it is the result of an ECDH key agreement step. This implie		selection. </dd>
	s that the AES HKDF version cannot be used with ECDH. If the extract step is ski		</dl>
	pped, the 'salt' value is not used as part of the HKDF functionality. </t>		<t indent="0" pn="section-5.1-4">HKDF is defined to use HMAC as the unde
	<t>The algorithms defined in this document are found in <xref target="x-		rlying PRF. However, it is
	table-hkdf"/>. </t>		possible to use other functions in the same construct to provide a
	<table anchor="x-table-hkdf" align="center">		different KDF that is more appropriate in the constrained world.
			Specifically, one can use AES-CBC-MAC as the PRF for the expand step,
	<name>HKDF Algorithms</name>		but not for the extract step. When using a good random shared secret
			of the correct length, the extract step can be skipped. For the AES
			algorithm versions, the extract step is always skipped. </t>
			<t indent="0" pn="section-5.1-5">The extract step cannot be skipped if t
			he secret is not uniformly
			random -- for example, if it is the result of an ECDH key agreement
			step. This implies that the AES HKDF version cannot be used with
			ECDH. If the extract step is skipped, the "salt" value is not used as
			part of the HKDF functionality. </t>
			<t indent="0" pn="section-5.1-6">The algorithms defined in this document
			are found in <xref target="x-table-hkdf" format="default" sectionFormat="of" de
			rivedContent="Table 8"/>. </t>
			<table anchor="x-table-hkdf" align="center" pn="table-8">
			<name slugifiedName="name-hkdf-algorithms">HKDF Algorithms</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>PRF</th>		<th align="left" colspan="1" rowspan="1">PRF</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>HKDF SHA-256</td>		<td align="left" colspan="1" rowspan="1">HKDF SHA-256</td>
	<td>HMAC with SHA-256</td>		<td align="left" colspan="1" rowspan="1">HMAC with SHA-256</td>
	<td>HKDF using HMAC SHA-256 as the PRF</td>		<td align="left" colspan="1" rowspan="1">HKDF using HMAC SHA-256 a
			s the PRF</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>HKDF SHA-512</td>		<td align="left" colspan="1" rowspan="1">HKDF SHA-512</td>
	<td>HMAC with SHA-512</td>		<td align="left" colspan="1" rowspan="1">HMAC with SHA-512</td>
	<td>HKDF using HMAC SHA-512 as the PRF</td>		<td align="left" colspan="1" rowspan="1">HKDF using HMAC SHA-512 a
			s the PRF</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>HKDF AES-MAC-128</td>		<td align="left" colspan="1" rowspan="1">HKDF AES-MAC-128</td>
	<td>AES-CBC-MAC-128</td>		<td align="left" colspan="1" rowspan="1">AES-CBC-MAC-128</td>
	<td>HKDF using AES-MAC as the PRF w/ 128-bit key</td>		<td align="left" colspan="1" rowspan="1">HKDF using AES-MAC as the
			PRF w/ 128-bit key</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>HKDF AES-MAC-256</td>		<td align="left" colspan="1" rowspan="1">HKDF AES-MAC-256</td>
	<td>AES-CBC-MAC-256</td>		<td align="left" colspan="1" rowspan="1">AES-CBC-MAC-256</td>
	<td>HKDF using AES-MAC as the PRF w/ 256-bit key</td>		<td align="left" colspan="1" rowspan="1">HKDF using AES-MAC as the
			PRF w/ 256-bit key</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<table anchor="HKDF_Alg_Params" align="center">		<table anchor="HKDF_Alg_Params" align="center" pn="table-9">
			<name slugifiedName="name-hkdf-algorithm-parameters">HKDF Algorithm Pa
	<name>HKDF Algorithm Parameters</name>		rameters</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Label</th>		<th align="left" colspan="1" rowspan="1">Label</th>
	<th>Type</th>		<th align="left" colspan="1" rowspan="1">Type</th>
	<th>Algorithm</th>		<th align="left" colspan="1" rowspan="1">Algorithm</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>salt</td>		<td align="left" colspan="1" rowspan="1">salt</td>
	<td>-20</td>		<td align="left" colspan="1" rowspan="1">-20</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>direct+HKDF-SHA-256, direct+HKDF-SHA-512, direct+HKDF-AES-128,		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-256, dire
	direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECDH-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH		ct+HKDF-SHA-512, direct+HKDF-AES-128, direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECD
	-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192KW, ECDH-ES+A256KW, ECDH-SS+A128KW, EC		H-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192K
	DH-SS+A192KW, ECDH-SS+A256KW </td>		W, ECDH-ES+A256KW, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
	<td>Random salt</td>		<td align="left" colspan="1" rowspan="1">Random salt</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	</section>		</section>
	<section anchor="context">		<section anchor="context" numbered="true" removeInRFC="false" toc="include
			" pn="section-5.2">
	<name>Context Information Structure</name>		<name slugifiedName="name-context-information-structu">Context Informati
	<t>The context information structure is used to ensure that the derived		on Structure</name>
	keying material is "bound" to the context of the transaction. The context infor		<t indent="0" pn="section-5.2-1">The context information structure is us
	mation structure used here is based on that defined in <xref target="SP800-56A"/		ed to ensure that the
	>. By using CBOR for the encoding of the context information structure, we auto		derived keying material is "bound" to the context of the transaction.
	matically get the same type and length separation of fields that is obtained by		The context information structure used here is based on that defined
	the use of ASN.1. This means that there is no need to encode the lengths for th		in <xref target="SP800-56A" format="default" sectionFormat="of" derivedCo
	e base elements, as it is done by the encoding used in JOSE (Section 4.6.2 of <x		ntent="SP800-56A"/>. By using CBOR for the encoding of the
	ref target="RFC7518"/>). </t>		context information structure, we automatically get the same type and
	<t>The context information structure refers to PartyU and PartyV as the		length separation of fields that is obtained by the use of ASN.1.
	two parties that are doing the key derivation. Unless the application protocol		This means that there is no need to encode the lengths for the base
	defines differently, we assign PartyU to the entity that is creating the message		elements, as it is done by the encoding used in JSON Object Signing
	and PartyV to the entity that is receiving the message. By doing this associat		and Encryption (JOSE) (<xref target="RFC7518" section="4.6.2" sectionForm
	ion, different keys will be derived for each direction as the context informatio		at="of" format="default" derivedLink="https://rfc-editor.org/rfc/rfc7518#section
	n is different in each direction. </t>		-4.6.2" derivedContent="RFC7518"/>).</t>
	<t>The context structure is built from information that is known to both		<t indent="0" pn="section-5.2-2">The context information structure refer
	entities. This information can be obtained from a variety of sources:		s to PartyU and PartyV as
			the two parties that are doing the key derivation. Unless the
			application protocol defines differently, we assign PartyU to the
			entity that is creating the message and PartyV to the entity that is
			receiving the message. By defining this association, different keys
			will be derived for each direction, as the context information is
			different in each direction.</t>
			<t indent="0" pn="section-5.2-3">The context structure is built from inf
			ormation that is known to both entities. This information can be obtained from
			a variety of sources:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-5
	<ul>		.2-4">
			<li pn="section-5.2-4.1">Fields can be defined by the application. Th
	<li>Fields can be defined by the application. This is commonly used t		is is commonly used to assign fixed names to parties, but it can be used for oth
	o assign fixed names to parties, but it can be used for other items such as nonc		er items such as nonces. </li>
	es. </li>		<li pn="section-5.2-4.2">Fields can be defined by usage of the output.
			Examples of this are the algorithm and key size that are being generated. </l
	<li>Fields can be defined by usage of the output. Examples of this ar		i>
	e the algorithm and key size that are being generated. </li>		<li pn="section-5.2-4.3">Fields can be defined by parameters from the
			message. We define
	<li>Fields can be defined by parameters from the message. We define a		a set of header parameters in <xref target="KDF_Context_Alg_Params" for
	set of header parameters in <xref target="KDF_Context_Alg_Params"/> that can be		mat="default" sectionFormat="of" derivedContent="Table 10"/> that can be used to
	used to carry the values associated with the context structure. Examples of th		carry the
	is are identities and nonce values. These header parameters are designed to be		values associated with the context structure. Examples of this are
	placed in the unprotected bucket of the recipient structure; they do not need to		identities and nonce values. These header parameters are designed
	be in the protected bucket since they already are included in the cryptographic		to be placed in the unprotected bucket of the recipient structure;
	computation by virtue of being included in the context structure. </li>		they do not need to be in the protected bucket, since they are already
			included in the cryptographic computation by virtue of being
			included in the context structure. </li>
	</ul>		</ul>
	<table anchor="KDF_Context_Alg_Params" align="center">		<table anchor="KDF_Context_Alg_Params" align="center" pn="table-10">
			<name slugifiedName="name-context-algorithm-parameter">Context Algorit
	<name>Context Algorithm Parameters</name>		hm Parameters</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Label</th>		<th align="left" colspan="1" rowspan="1">Label</th>
	<th>Type</th>		<th align="left" colspan="1" rowspan="1">Type</th>
	<th>Algorithm</th>		<th align="left" colspan="1" rowspan="1">Algorithm</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>PartyU identity</td>		<td align="left" colspan="1" rowspan="1">PartyU identity</td>
	<td>-21</td>		<td align="left" colspan="1" rowspan="1">-21</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>direct+HKDF-SHA-256, direct+HKDF-SHA-512, direct+HKDF-AES-128,		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-256, dire
	direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECDH-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH		ct+HKDF-SHA-512, direct+HKDF-AES-128, direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECD
	-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192KW, ECDH-ES+A256KW, ECDH-SS+A128KW, EC		H-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192K
	DH-SS+A192KW, ECDH-SS+A256KW </td>		W, ECDH-ES+A256KW, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
	<td>Party U identity information</td>		<td align="left" colspan="1" rowspan="1">PartyU identity informati
			on</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>PartyU nonce</td>		<td align="left" colspan="1" rowspan="1">PartyU nonce</td>
	<td>-22</td>		<td align="left" colspan="1" rowspan="1">-22</td>
	<td>bstr / int</td>		<td align="left" colspan="1" rowspan="1">bstr / int</td>
	<td>direct+HKDF-SHA-256, direct+HKDF-SHA-512, direct+HKDF-AES-128,		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-256, dire
	direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECDH-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH		ct+HKDF-SHA-512, direct+HKDF-AES-128, direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECD
	-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192KW, ECDH-ES+A256KW, ECDH-SS+A128KW, EC		H-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192K
	DH-SS+A192KW, ECDH-SS+A256KW </td>		W, ECDH-ES+A256KW, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
	<td>Party U provided nonce</td>		<td align="left" colspan="1" rowspan="1">PartyU provided nonce</td
			>
	</tr>		</tr>
	<tr>		<tr>
	<td>PartyU other</td>		<td align="left" colspan="1" rowspan="1">PartyU other</td>
	<td>-23</td>		<td align="left" colspan="1" rowspan="1">-23</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>direct+HKDF-SHA-256, direct+HKDF-SHA-512, direct+HKDF-AES-128,		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-256, dire
	direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECDH-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH		ct+HKDF-SHA-512, direct+HKDF-AES-128, direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECD
	-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192KW, ECDH-ES+A256KW, ECDH-SS+A128KW, EC		H-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192K
	DH-SS+A192KW, ECDH-SS+A256KW </td>		W, ECDH-ES+A256KW, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
	<td>Party U other provided information</td>		<td align="left" colspan="1" rowspan="1">PartyU other provided inf
			ormation</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>PartyV identity</td>		<td align="left" colspan="1" rowspan="1">PartyV identity</td>
	<td>-24</td>		<td align="left" colspan="1" rowspan="1">-24</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>direct+HKDF-SHA-256, direct+HKDF-SHA-512, direct+HKDF-AES-128,		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-256, dire
	direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECDH-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH		ct+HKDF-SHA-512, direct+HKDF-AES-128, direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECD
	-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192KW, ECDH-ES+A256KW, ECDH-SS+A128KW, EC		H-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192K
	DH-SS+A192KW, ECDH-SS+A256KW </td>		W, ECDH-ES+A256KW, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
	<td>Party V identity information</td>		<td align="left" colspan="1" rowspan="1">PartyV identity informati
			on</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>PartyV nonce</td>		<td align="left" colspan="1" rowspan="1">PartyV nonce</td>
	<td>-25</td>		<td align="left" colspan="1" rowspan="1">-25</td>
	<td>bstr / int</td>		<td align="left" colspan="1" rowspan="1">bstr / int</td>
	<td>direct+HKDF-SHA-256, direct+HKDF-SHA-512, direct+HKDF-AES-128,		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-256, dire
	direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECDH-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH		ct+HKDF-SHA-512, direct+HKDF-AES-128, direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECD
	-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192KW, ECDH-ES+A256KW, ECDH-SS+A128KW, EC		H-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192K
	DH-SS+A192KW, ECDH-SS+A256KW </td>		W, ECDH-ES+A256KW, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
	<td>Party V provided nonce</td>		<td align="left" colspan="1" rowspan="1">PartyV provided nonce</td
			>
	</tr>		</tr>
	<tr>		<tr>
	<td>PartyV other</td>		<td align="left" colspan="1" rowspan="1">PartyV other</td>
	<td>-26</td>		<td align="left" colspan="1" rowspan="1">-26</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>direct+HKDF-SHA-256, direct+HKDF-SHA-512, direct+HKDF-AES-128,		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-256, dire
	direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECDH-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH		ct+HKDF-SHA-512, direct+HKDF-AES-128, direct+HKDF-AES-256, ECDH-ES+HKDF-256, ECD
	-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192KW, ECDH-ES+A256KW, ECDH-SS+A128KW, EC		H-ES+HKDF-512, ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192K
	DH-SS+A192KW, ECDH-SS+A256KW </td>		W, ECDH-ES+A256KW, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
	<td>Party V other provided information</td>		<td align="left" colspan="1" rowspan="1">PartyV other provided inf
			ormation</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>We define a CBOR object to hold the context information. This object is referred to as COSE_KDF_Context. The object is based on a CBOR array type. The fields in the array are:		<t indent="0" pn="section-5.2-6">We define a CBOR object to hold the con text information. This object is referred to as COSE_KDF_Context. The object i s based on a CBOR array type. The fields in the array are:
	</t>		</t>
			<dl newline="false" indent="3" spacing="normal" pn="section-5.2-7">
	<dl newline="false">		<dt pn="section-5.2-7.1">AlgorithmID:</dt>
	<dt>AlgorithmID:</dt>		<dd pn="section-5.2-7.2">
	<dd>
	This field indicates the algorithm for which the key material will b e used.		This field indicates the algorithm for which the key material will b e used.
	This normally is either a key wrap algorithm identifier or a content		This normally is either a key wrap algorithm identifier or a
	encryption algorithm identifier.		content encryption algorithm identifier.
	The values are from the "COSE Algorithms" registry.		The values are from the "COSE Algorithms" registry.
	This field is required to be present.		This field is required to be present.
	The field exists in the context information so that a different key is generated for each algorithm even of all of the other context information is the same.		The field exists in the context information so that a different key is generated for each algorithm even if all of the other context information is the same.
	In practice, this means if algorithm A is broken and thus finding th e key is relatively easy, the key derived for algorithm B will not be the same a s the key derived for algorithm A.		In practice, this means if algorithm A is broken and thus finding th e key is relatively easy, the key derived for algorithm B will not be the same a s the key derived for algorithm A.
	</dd>		</dd>
			<dt pn="section-5.2-7.3">PartyUInfo:</dt>
	<dt>PartyUInfo:</dt>		<dd pn="section-5.2-7.4">
			<t indent="0" pn="section-5.2-7.4.1">This field holds information ab
	<dd>		out PartyU. The PartyUInfo is
	<t>This field holds information about party U. The PartyUInfo is en		encoded as a CBOR array. The elements of PartyUInfo are encoded
	coded as a CBOR array. The elements of PartyUInfo are encoded in the order pres		in the order presented below. The elements of the PartyUInfo
	ented below. The elements of the PartyUInfo array are:		array are:
	</t>		</t>
			<dl newline="false" indent="3" spacing="normal" pn="section-5.2-7.4.
	<dl newline="false">		2">
	<dt>identity:</dt>		<dt pn="section-5.2-7.4.2.1">identity:</dt>
			<dd pn="section-5.2-7.4.2.2">
	<dd>		<t indent="0" pn="section-5.2-7.4.2.2.1">This contains the ident
	<t>This contains the identity information for party U. The iden		ity information for PartyU. The
	tities can be assigned in one of two manners. First, a protocol can assign iden		identities can be assigned in one of two manners. First, a
	tities based on roles. For example, the roles of "client" and "server" may be a		protocol can assign identities based on roles. For example,
	ssigned to different entities in the protocol. Each entity would then use the c		the roles of "client" and "server" may be assigned to
	orrect label for the data they send or receive. The second way for a protocol t		different entities in the protocol. Each entity would then
	o assign identities is to use a name based on a naming system (i.e., DNS, X.509		use the correct label for the data it sends or receives. The
	names).		second way for a protocol to assign identities is to use a
			name based on a naming system (i.e., DNS or X.509 names).
			</t>
			<t indent="0" pn="section-5.2-7.4.2.2.2"> We define an algorithm
			parameter, "PartyU identity", that
			can be used to carry identity information in the message.
			However, identity information is often known as part of the
			protocol and can thus be inferred rather than made explicit.
			If identity information is carried in the message,
			applications <bcp14>SHOULD</bcp14> have a way of validating
			the supplied identity information. The identity information
			does not need to be specified and is set to nil in that case.
	</t>		</t>
	<t> We define an algorithm parameter 'PartyU identity' that can be used to carry identity information in the message. However, identity informa tion is often known as part of the protocol and can thus be inferred rather than made explicit. If identity information is carried in the message, applications <bcp14>SHOULD</bcp14> have a way of validating the supplied identity informatio n. The identity information does not need to be specified and is set to nil in that case. </t>
	</dd>		</dd>
	<dt>nonce:</dt>		<dt pn="section-5.2-7.4.2.3">nonce:</dt>
			<dd pn="section-5.2-7.4.2.4">
	<dd>		<t indent="0" pn="section-5.2-7.4.2.4.1">This contains a nonce v
	<t>This contains a nonce value. The nonce can either be implici		alue. The nonce can be either
	t from the protocol or be carried as a value in the unprotected header bucket.		implicit from the protocol or carried as a value in the
			unprotected header bucket.
	</t>		</t>
	<t> We define an algorithm parameter 'PartyU nonce' that can be		<t indent="0" pn="section-5.2-7.4.2.4.2"> We define an algorithm
	used to carry this value in the message; however, the nonce value could be deter		parameter, "PartyU nonce", that can be used to carry this value in the message;
	mined by the application and the value determined from elsewhere.		however, the nonce value could be determined by the application and its
			value obtained in a different manner.
	</t>		</t>
	<t> This option does not need to be specified and is set to nil		<t indent="0" pn="section-5.2-7.4.2.4.3"> This option does not n
	in that case. </t>		eed to be specified; if not
			needed, it is set to nil. </t>
	</dd>		</dd>
	<dt>other:</dt>		<dt pn="section-5.2-7.4.2.5">other:</dt>
			<dd pn="section-5.2-7.4.2.6">This contains other information that
	<dd>This contains other information that is defined by the protoco		is defined by the protocol. This option does not need to be specified; if not ne
	l. This option does not need to be specified and is set to nil in that case. </d		eded, it is set to nil. </dd>
	d>
	</dl>		</dl>
	</dd>		</dd>
	<dt>PartyVInfo:</dt>		<dt pn="section-5.2-7.5">PartyVInfo:</dt>
			<dd pn="section-5.2-7.6">This field holds information about PartyV. T
	<dd>This field holds information about party V. The content of the st		he content of the structure is the same as for the PartyUInfo but for PartyV. <
	ructure is the same as for the PartyUInfo but for party V. </dd>		/dd>
	<dt>SuppPubInfo:</dt>		<dt pn="section-5.2-7.7">SuppPubInfo:</dt>
			<dd pn="section-5.2-7.8">
	<dd>		<t indent="0" pn="section-5.2-7.8.1">This field contains public info
	<t>This field contains public information that is mutually known to		rmation that is mutually known to both parties, and is encoded as a CBOR array.
	both parties.
	</t>		</t>
			<dl newline="false" indent="3" spacing="normal" pn="section-5.2-7.8.
	<dl newline="false">		2">
	<dt>keyDataLength:</dt>		<dt pn="section-5.2-7.8.2.1">keyDataLength:</dt>
			<dd pn="section-5.2-7.8.2.2">This is set to the number of bits of
	<dd>This is set to the number of bits of the desired output value.		the desired output
	This practice means if algorithm A can use two different key lengths, the key		value. This practice means if algorithm A can use two different
	derived for longer key size will not contain the key for shorter key size as a p		key lengths, the key derived for the longer key size will not
	refix. </dd>		contain the key for the shorter key size as a prefix. </dd>
	<dt>protected:</dt>		<dt pn="section-5.2-7.8.2.3">protected:</dt>
			<dd pn="section-5.2-7.8.2.4">This field contains the protected par
	<dd>This field contains the protected parameter field. If there a		ameter field. If there
	re no elements in the protected field, then use a zero-length bstr. </dd>		are no elements in the "protected" field, then use a zero-length
	<dt>other:</dt>		bstr. </dd>
			<dt pn="section-5.2-7.8.2.5">other:</dt>
	<dd>This field is for free form data defined by the application.		<dd pn="section-5.2-7.8.2.6">This field is for free-form data defi
	An example is that an application could define two different byte strings to be		ned by the application.
	placed here to generate different keys for a data stream versus a control stream		For example, an application could define two different
	. This field is optional and will only be present if the application defines a		byte strings to be placed here to generate different keys for a
	structure for this information. Applications that define this <bcp14>SHOULD</bc		data stream versus a control stream. This field is optional and
	p14> use CBOR to encode the data so that types and lengths are correctly include		will only be present if the application defines a structure for
	d. </dd>		this information. Applications that define this
			<bcp14>SHOULD</bcp14> use CBOR to encode the data so that types
			and lengths are correctly included. </dd>
	</dl>		</dl>
	</dd>		</dd>
	<dt>SuppPrivInfo:</dt>		<dt pn="section-5.2-7.9">SuppPrivInfo:</dt>
			<dd pn="section-5.2-7.10">This field contains private information that
	<dd>This field contains private information that is mutually known pri		is mutually known private information. An example of this information would be
	vate information. An example of this information would be a preexisting shared		a pre-existing shared secret. (This could, for example, be used in combination
	secret. (This could, for example, be used in combination with an ECDH key agree		with an ECDH key agreement to provide a secondary proof of identity.) The field
	ment to provide a secondary proof of identity.) The field is optional and will o		is optional and will only be present if the application defines a structure for
	nly be present if the application defines a structure for this information. App		this information. Applications that define this <bcp14>SHOULD</bcp14> use CBOR
	lications that define this <bcp14>SHOULD</bcp14> use CBOR to encode the data so		to encode the data so that types and lengths are correctly included. </dd>
	that types and lengths are correctly included. </dd>
	</dl>		</dl>
	<t>The following CDDL fragment corresponds to the text above. </t>		<t indent="0" pn="section-5.2-8">The following CDDL fragment corresponds
	<artwork type="CDDL" name="" alt=""><![CDATA[		to the text above. </t>
			<sourcecode type="cddl" markers="false" pn="section-5.2-9">
	PartyInfo = (		PartyInfo = (
	identity : bstr / nil,		identity : bstr / nil,
	nonce : bstr / int / nil,		nonce : bstr / int / nil,
	other : bstr / nil		other : bstr / nil
	)		)
	COSE_KDF_Context = [		COSE_KDF_Context = [
	AlgorithmID : int / tstr,		AlgorithmID : int / tstr,
	PartyUInfo : [ PartyInfo ],		PartyUInfo : [ PartyInfo ],
	PartyVInfo : [ PartyInfo ],		PartyVInfo : [ PartyInfo ],
	SuppPubInfo : [		SuppPubInfo : [
	keyDataLength : uint,		keyDataLength : uint,
	protected : empty_or_serialized_map,		protected : empty_or_serialized_map,
	? other : bstr		? other : bstr
	],		],
	? SuppPrivInfo : bstr		? SuppPrivInfo : bstr
	]		]
	]]></artwork>		</sourcecode>
	</section>		</section>
	</section>		</section>
	<section anchor="key-management-algs">		<section anchor="key-management-algs" numbered="true" removeInRFC="false" to
			c="include" pn="section-6">
			<name slugifiedName="name-content-key-distribution-me">Content Key Distrib
			ution Methods</name>
			<t indent="0" pn="section-6-1">
	<name>Content Key Distribution Methods</name>		<xref section="8.5" target="RFC9052" sectionFormat="of" format="default"
	<t>		derivedLink="https://rfc-editor.org/rfc/rfc9052#section-8.5" derivedContent="RF
	<relref section="&CKeyDistributeSection;" target="I-D.ietf-cose-rfc8152b		C9052"/> contains a generic description of content key distribution methods.
	is-struct"/> contains a generic description of content key distribution methods.
	This document defines the identifiers and usage for a number of content key distribution methods.		This document defines the identifiers and usage for a number of content key distribution methods.
	</t>		</t>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-6.1
	<name>Direct Encryption</name>		">
	<t>		<name slugifiedName="name-direct-encryption">Direct Encryption</name>
	Direct encryption algorithm is defined in <relref section="&DirectDist		<t indent="0" pn="section-6.1-1">
	ribute;" target="I-D.ietf-cose-rfc8152bis-struct"/>.		A direct encryption algorithm is defined in <xref section="8.5.1" targ
	Information about how to fill in the COSE_Recipient structure are deta		et="RFC9052" sectionFormat="of" format="default" derivedLink="https://rfc-editor
	iled there.		.org/rfc/rfc9052#section-8.5.1" derivedContent="RFC9052"/>.
			Information about how to fill in the COSE_Recipient structure is detai
			led there.
	</t>		</t>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-6
			.1.1">
	<name>Direct Key</name>		<name slugifiedName="name-direct-key">Direct Key</name>
	<t>		<t indent="0" pn="section-6.1.1-1">
	This recipient algorithm is the simplest; the identified key is direct ly used as the key for the next layer down in the message.		This recipient algorithm is the simplest; the identified key is direct ly used as the key for the next layer down in the message.
	There are no algorithm parameters defined for this algorithm.		There are no algorithm parameters defined for this algorithm.
	The algorithm identifier value is assigned in <xref target="x-table-d irect"/>.		The algorithm identifier value is assigned in <xref target="x-table-d irect" format="default" sectionFormat="of" derivedContent="Table 11"/>.
	</t>		</t>
	<t>		<t indent="0" pn="section-6.1.1-2">
	When this algorithm is used, the protected field <bcp14>MUST</bcp14> b		When this algorithm is used, the "protected" field
	e zero length.		<bcp14>MUST</bcp14> be zero length.
	The key type <bcp14>MUST</bcp14> be 'Symmetric'.		The key type <bcp14>MUST</bcp14> be "Symmetric".
	</t>		</t>
	<table anchor="x-table-direct" align="center">		<table anchor="x-table-direct" align="center" pn="table-11">
			<name slugifiedName="name-direct-key-2">Direct Key</name>
	<name>Direct Key</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>direct</td>		<td align="left" colspan="1" rowspan="1">direct</td>
	<td>-6</td>		<td align="center" colspan="1" rowspan="1">-6</td>
	<td>Direct use of CEK</td>		<td align="left" colspan="1" rowspan="1">Direct use of content e
			ncryption key (CEK)</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<section>		<section numbered="true" removeInRFC="false" toc="exclude" pn="section
			-6.1.1.1">
	<name>Security Considerations for Direct Key</name>		<name slugifiedName="name-security-considerations-for-d">Security Co
	<t>This recipient algorithm has several potential problems that need		nsiderations for Direct Key</name>
	to be considered:		<t indent="0" pn="section-6.1.1.1-1">This recipient algorithm has se
			veral potential problems that need to be considered:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="secti
	<ul>		on-6.1.1.1-2">
			<li pn="section-6.1.1.1-2.1">These keys need to have some method o
	<li>These keys need to have some method to be regularly updated ov		f being regularly updated over time. All of the content encryption algorithms s
	er time. All of the content encryption algorithms specified in this document ha		pecified in this document have limits on how many times a key can be used withou
	ve limits on how many times a key can be used without significant loss of securi		t significant loss of security. </li>
	ty. </li>		<li pn="section-6.1.1.1-2.2">These keys need to be dedicated to a
			single algorithm. There have been a number of attacks developed over time when
	<li>These keys need to be dedicated to a single algorithm. There		a single key is used for multiple different algorithms. One example of this is
	have been a number of attacks developed over time when a single key is used for		the use of a single key for both the CBC encryption mode and the CBC-MAC authent
	multiple different algorithms. One example of this is the use of a single key f		ication mode. </li>
	or both the CBC encryption mode and the CBC-MAC authentication mode. </li>		<li pn="section-6.1.1.1-2.3">Breaking one message means all messag
			es are broken. If an adversary succeeds in determining the key for a single mes
	<li>Breaking one message means all messages are broken. If an adv		sage, then the key for all messages is also determined. </li>
	ersary succeeds in determining the key for a single message, then the key for al
	l messages is also determined. </li>
	</ul>		</ul>
	</section>		</section>
	</section>		</section>
	<section anchor="direct-kdf">		<section anchor="direct-kdf" numbered="true" removeInRFC="false" toc="in
			clude" pn="section-6.1.2">
	<name>Direct Key with KDF</name>		<name slugifiedName="name-direct-key-with-kdf">Direct Key with KDF</na
	<t>These recipient algorithms take a common shared secret between the		me>
	two parties and applies the HKDF function (<xref target="HKDF-section"/>), using		<t indent="0" pn="section-6.1.2-1">These recipient algorithms take a c
	the context structure defined in <xref target="context"/> to transform the shar		ommon shared secret between
	ed secret into the CEK.		the two parties and apply the HKDF function (<xref target="HKDF-section
			" format="default" sectionFormat="of" derivedContent="Section 5.1"/>), using the
	The 'protected' field can be of non-zero length. Either the 'salt' para		context structure defined in
	meter of HKDF or the 'PartyU nonce' parameter of the context structure <bcp14>MU		<xref target="context" format="default" sectionFormat="of" derivedConte
	ST</bcp14> be present. The salt/nonce parameter can be generated either randoml		nt="Section 5.2"/> to transform the shared secret into the
	y or deterministically. The requirement is that it be a unique value for the sh		CEK. The "protected" field can be of nonzero length. Either
	ared secret in question. </t>		the "salt" parameter for HKDF (<xref target="HKDF_Alg_Params" format="
	<t>If the salt/nonce value is generated randomly, then it is suggested		default" sectionFormat="of" derivedContent="Table 9"/>) or the "PartyU nonce" pa
	that the length of the random value be the same length as the output of the has		rameter
	h function underlying HKDF. While there is no way to guarantee that it will be		for the context structure (<xref target="KDF_Context_Alg_Params" forma
	unique, there is a high probability that it will be unique. If the salt/nonce v		t="default" sectionFormat="of" derivedContent="Table 10"/>) <bcp14>MUST</bcp14>
	alue is generated deterministically, it can be guaranteed to be unique, and thus		be
	there is no length requirement. </t>		present (both can be present if desired). The value in the
	<t>A new IV must be used for each message if the same key is used. Th		"salt"/"nonce" parameter
	e IV can be modified in a predictable manner, a random manner, or an unpredictab		can be generated either randomly or deterministically. The
	le manner (i.e., encrypting a counter). </t>		requirement is that it be a unique value for the shared secret in
	<t>The IV used for a key can also be generated from the same HKDF func		question. </t>
	tionality as the key is generated. If HKDF is used for generating the IV, the a		<t indent="0" pn="section-6.1.2-2">If the salt/nonce value is generate
	lgorithm identifier is set to "IV-GENERATION". </t>		d randomly, then it is suggested that the length of the random value be the same
			length as the output of the hash function underlying HKDF. While there is no w
	<t>The set of algorithms defined in this document can be found in <xre		ay to guarantee that it will be unique, there is a high probability that it will
	f target="x-table-direct-kdf"/>. </t>		be unique. If the salt/nonce value is generated deterministically, it can be g
			uaranteed to be unique, and thus there is no length requirement. </t>
	<table anchor="x-table-direct-kdf" align="center">		<t indent="0" pn="section-6.1.2-3">A new IV must be used for each mess
			age if the same key is used. The IV can be modified in a predictable manner, a
	<name>Direct Key with KDF</name>		random manner, or an unpredictable manner (e.g., encrypting a counter). </t>
			<t indent="0" pn="section-6.1.2-4">The IV used for a key can also be g
			enerated using the same HKDF
			functionality used to generate the key. If HKDF is used for
			generating the IV, the algorithm identifier is set to 34
			("IV-GENERATION"). </t>
			<t indent="0" pn="section-6.1.2-5">The set of algorithms defined in th
			is document can be found in <xref target="x-table-direct-kdf" format="default" s
			ectionFormat="of" derivedContent="Table 12"/>. </t>
			<table anchor="x-table-direct-kdf" align="center" pn="table-12">
			<name slugifiedName="name-direct-key-with-kdf-2">Direct Key with KDF
			</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>KDF</th>		<th align="left" colspan="1" rowspan="1">KDF</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>direct+HKDF-SHA-256</td>		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-256</td
	<td>-10</td>		>
	<td>HKDF SHA-256</td>		<td align="center" colspan="1" rowspan="1">-10</td>
	<td>Shared secret w/ HKDF and SHA-256</td>		<td align="left" colspan="1" rowspan="1">HKDF SHA-256</td>
			<td align="left" colspan="1" rowspan="1">Shared secret w/ HKDF a
			nd SHA-256</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>direct+HKDF-SHA-512</td>		<td align="left" colspan="1" rowspan="1">direct+HKDF-SHA-512</td
	<td>-11</td>		>
	<td>HKDF SHA-512</td>		<td align="center" colspan="1" rowspan="1">-11</td>
	<td>Shared secret w/ HKDF and SHA-512</td>		<td align="left" colspan="1" rowspan="1">HKDF SHA-512</td>
			<td align="left" colspan="1" rowspan="1">Shared secret w/ HKDF a
			nd SHA-512</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>direct+HKDF-AES-128</td>		<td align="left" colspan="1" rowspan="1">direct+HKDF-AES-128</td
	<td>-12</td>		>
	<td>HKDF AES-MAC-128</td>		<td align="center" colspan="1" rowspan="1">-12</td>
	<td>Shared secret w/ AES-MAC 128-bit key</td>		<td align="left" colspan="1" rowspan="1">HKDF AES-MAC-128</td>
			<td align="left" colspan="1" rowspan="1">Shared secret w/ AES-MA
			C 128-bit key</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>direct+HKDF-AES-256</td>		<td align="left" colspan="1" rowspan="1">direct+HKDF-AES-256</td
	<td>-13</td>		>
	<td>HKDF AES-MAC-256</td>		<td align="center" colspan="1" rowspan="1">-13</td>
	<td>Shared secret w/ AES-MAC 256-bit key</td>		<td align="left" colspan="1" rowspan="1">HKDF AES-MAC-256</td>
			<td align="left" colspan="1" rowspan="1">Shared secret w/ AES-MA
			C 256-bit key</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>When using a COSE key for this algorithm, the following checks are made:		<t indent="0" pn="section-6.1.2-7">When using a COSE key for this algo rithm, the following checks are made:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section
	<ul>		-6.1.2-8">
			<li pn="section-6.1.2-8.1">The "kty" field <bcp14>MUST</bcp14> be pr
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MU		esent, and it <bcp14>MUST</bcp14> be "Symmetric".</li>
	ST</bcp14> be 'Symmetric'.</li>		<li pn="section-6.1.2-8.2">If the "alg" field is present, it <bcp14>
			MUST</bcp14> match the algorithm being used.</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the		<li pn="section-6.1.2-8.3">If the "key_ops" field is present, it <bc
	algorithm being used.</li>		p14>MUST</bcp14> include "derive key" or "derive bits".</li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> includ
	e 'deriveKey' or 'deriveBits'.</li>
	</ul>		</ul>
	<section>		<section numbered="true" removeInRFC="false" toc="exclude" pn="section
			-6.1.2.1">
	<name>Security Considerations for Direct Key with KDF</name>		<name slugifiedName="name-security-considerations-for-di">Security C
	<t>The shared secret needs to have some method to be regularly updat		onsiderations for Direct Key with KDF</name>
	ed over time. The shared secret forms the basis of trust. Although not used di		<t indent="0" pn="section-6.1.2.1-1">The shared secret needs to have
	rectly, it should still be subject to scheduled rotation. </t>		some method of being regularly
	<t>While these methods do not provide for perfect forward secrecy, a		updated over time. The shared secret forms the basis of trust.
	s the same shared secret is used for all of the keys generated, if the key for a		Although not used directly, it should still be subject to
	ny single message is discovered, only the message (or series of messages) using		scheduled rotation. </t>
	that derived key are compromised. A new key derivation step will generate a new		<t indent="0" pn="section-6.1.2.1-2">These methods do not provide fo
	key that requires the same amount of work to get the key. </t>		r perfect forward secrecy, as
			the same shared secret is used for all of the keys generated;
			however, if the key for any single message is discovered, only the
			message or series of messages using that derived key are
			compromised. A new key derivation step will generate a new key that
			requires the same
			amount of work to get the key. </t>
	</section>		</section>
	</section>		</section>
	</section>		</section>
	<section anchor="key_wrap_algs">		<section anchor="key_wrap_algs" numbered="true" removeInRFC="false" toc="i
	<name>Key Wrap</name>		nclude" pn="section-6.2">
	<t>		<name slugifiedName="name-key-wrap">Key Wrap</name>
	Key wrap is defined in <relref section="&DirectDistribute;" target="I		<t indent="0" pn="section-6.2-1">
	-D.ietf-cose-rfc8152bis-struct"/>.		Key wrap is defined in <xref section="8.5.2" target="RFC9052" section
			Format="of" format="default" derivedLink="https://rfc-editor.org/rfc/rfc9052#sec
			tion-8.5.2" derivedContent="RFC9052"/>.
	Information about how to fill in the COSE_Recipient structure is detai led there.		Information about how to fill in the COSE_Recipient structure is detai led there.
	</t>		</t>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-6
	<section>		.2.1">
	<name>AES Key Wrap</name>		<name slugifiedName="name-aes-key-wrap">AES Key Wrap</name>
	<t>The AES Key Wrap algorithm is defined in <xref target="RFC3394"/>. T		<t indent="0" pn="section-6.2.1-1">The AES Key Wrap algorithm is defin
	his algorithm uses an AES key to wrap a value that is a multiple of 64 bits. As		ed in <xref target="RFC3394" format="default" sectionFormat="of" derivedContent=
	such, it can be used to wrap a key for any of the content encryption algorithms		"RFC3394"/>.
	defined in this document. The algorithm requires a single fixed parameter, the		This algorithm uses an AES key to wrap a value that is a multiple of
	initial value. This is fixed to the value specified in Section 2.2.3.1 of <xre		64 bits. As such, it can be used to wrap a key for any of the
	f target="RFC3394"/>. There are no public key parameters that vary on a per-inv		content encryption algorithms defined in this document. The algorithm
	ocation basis. The protected header bucket <bcp14>MUST</bcp14> be empty. </t>		requires a single fixed parameter, the initial value. This is fixed
	<t>Keys may be obtained either from a key structure or from a recipient		to the value specified in <xref target="RFC3394" section="2.2.3.1" sectio
	structure. Implementations encrypting and decrypting <bcp14>MUST</bcp14> valida		nFormat="of" format="default" derivedLink="https://rfc-editor.org/rfc/rfc3394#se
	te that the key type, key length, and algorithm are correct and appropriate for		ction-2.2.3.1" derivedContent="RFC3394"/>. There are no public key parameters t
	the entities involved. </t>		hat vary on
	<t>When using a COSE key for this algorithm, the following checks are ma		a per-invocation basis. The protected header bucket
	de:		<bcp14>MUST</bcp14> be empty. </t>
	</t>		<t indent="0" pn="section-6.2.1-2">Keys may be obtained from either a
			key structure or a recipient
	<ul>		structure. Implementations that are encrypting or decrypting
			<bcp14>MUST</bcp14> validate that the key type, key length, and
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		algorithm are correct and appropriate for the entities involved. </t>
	</bcp14> be 'Symmetric'.</li>		<t indent="0" pn="section-6.2.1-3">When using a COSE key for this algo
			rithm, the following checks are made:
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the AE		</t>
	S Key Wrap algorithm being used.</li>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="section
			-6.2.1-4">
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		<li pn="section-6.2.1-4.1">The "kty" field <bcp14>MUST</bcp14> be pr
	'encrypt' or 'wrap key' when encrypting.</li>		esent, and it <bcp14>MUST</bcp14> be "Symmetric".</li>
			<li pn="section-6.2.1-4.2">If the "alg" field is present, it <bcp14>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		MUST</bcp14> match the AES Key Wrap algorithm being used.</li>
	'decrypt' or 'unwrap key' when decrypting.</li>		<li pn="section-6.2.1-4.3">If the "key_ops" field is present, it <bc
	</ul>		p14>MUST</bcp14> include "encrypt" or "wrap key" when encrypting.</li>
	<table anchor="x-table_aes_keywrap" align="center">		<li pn="section-6.2.1-4.4">If the "key_ops" field is present, it <bc
			p14>MUST</bcp14> include "decrypt" or "unwrap key" when decrypting.</li>
	<name>AES Key Wrap Algorithm Values</name>		</ul>
	<thead>		<table anchor="x-table_aes_keywrap" align="center" pn="table-13">
	<tr>		<name slugifiedName="name-aes-key-wrap-algorithm-valu">AES Key Wrap
	<th>Name</th>		Algorithm Values</name>
	<th>Value</th>		<thead>
	<th>Key Size</th>		<tr>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	</tr>		<th align="center" colspan="1" rowspan="1">Value</th>
	</thead>		<th align="center" colspan="1" rowspan="1">Key Size</th>
	<tbody>		<th align="left" colspan="1" rowspan="1">Description</th>
	<tr>		</tr>
	<td>A128KW</td>		</thead>
	<td>-3</td>		<tbody>
	<td>128</td>		<tr>
	<td>AES Key Wrap w/ 128-bit key</td>		<td align="left" colspan="1" rowspan="1">A128KW</td>
	</tr>		<td align="center" colspan="1" rowspan="1">-3</td>
	<tr>		<td align="center" colspan="1" rowspan="1">128</td>
	<td>A192KW</td>		<td align="left" colspan="1" rowspan="1">AES Key Wrap w/ 128-bit
	<td>-4</td>		key</td>
	<td>192</td>		</tr>
	<td>AES Key Wrap w/ 192-bit key</td>		<tr>
	</tr>		<td align="left" colspan="1" rowspan="1">A192KW</td>
	<tr>		<td align="center" colspan="1" rowspan="1">-4</td>
	<td>A256KW</td>		<td align="center" colspan="1" rowspan="1">192</td>
	<td>-5</td>		<td align="left" colspan="1" rowspan="1">AES Key Wrap w/ 192-bit
	<td>256</td>		key</td>
	<td>AES Key Wrap w/ 256-bit key</td>		</tr>
	</tr>		<tr>
	</tbody>		<td align="left" colspan="1" rowspan="1">A256KW</td>
	</table>		<td align="center" colspan="1" rowspan="1">-5</td>
	<section>		<td align="center" colspan="1" rowspan="1">256</td>
			<td align="left" colspan="1" rowspan="1">AES Key Wrap w/ 256-bit
	<name>Security Considerations for AES-KW</name>		key</td>
	<t>The shared secret needs to have some method to be regularly updated		</tr>
	over time. The shared secret is the basis of trust. </t>		</tbody>
	</section>		</table>
			<section numbered="true" removeInRFC="false" toc="exclude" pn="section
			-6.2.1.1">
			<name slugifiedName="name-security-considerations-for-aes-">Security
			Considerations for AES Key Wrap</name>
			<t indent="0" pn="section-6.2.1.1-1">The shared secret needs to have
			some method of being regularly updated over time. The shared secret is the bas
			is of trust. </t>
			</section>
	</section>		</section>
	</section>		</section>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-6.3
	<section>		">
	<name>Direct Key Agreement</name>		<name slugifiedName="name-direct-key-agreement">Direct Key Agreement</na
			me>
	<t>		<t indent="0" pn="section-6.3-1">
	Key Transport is defined in <relref section="9.5.4" target="I-D.ietf-c		Direct Key Agreement is defined in <xref section="8.5.4" target="RFC90
	ose-rfc8152bis-struct"/>.		52" sectionFormat="of" format="default" derivedLink="https://rfc-editor.org/rfc/
			rfc9052#section-8.5.4" derivedContent="RFC9052"/>.
	Information about how to fill in the COSE_Recipient structure is detai led there.		Information about how to fill in the COSE_Recipient structure is detai led there.
	</t>		</t>
			<section anchor="ECDH" numbered="true" removeInRFC="false" toc="include"
	<section anchor="ECDH">		pn="section-6.3.1">
			<name slugifiedName="name-direct-ecdh">Direct ECDH</name>
	<name>Direct ECDH</name>		<t indent="0" pn="section-6.3.1-1">The mathematics for ECDH can be fou
	<t>The mathematics for ECDH can be found in <xref target="RFC6090"/>. I		nd in <xref target="RFC6090" format="default" sectionFormat="of" derivedContent=
	n this document, the algorithm is extended to be used with the two curves define		"RFC6090"/>. In this document, the algorithm is extended to be used with the tw
	d in <xref target="RFC7748"/>. </t>		o curves defined in <xref target="RFC7748" format="default" sectionFormat="of" d
	<t>ECDH is parameterized by the following:		erivedContent="RFC7748"/>. </t>
	</t>		<t indent="0" pn="section-6.3.1-2">ECDH is parameterized by the follow
			ing:
	<ul>		</t>
			<dl indent="3" newline="false" spacing="normal" pn="section-6.3.1-3">
	<li>		<dt pn="section-6.3.1-3.1">Curve Type/Curve:</dt>
	<t>Curve Type/Curve: The curve selected controls not only the size o		<dd pn="section-6.3.1-3.2">
	f the shared secret, but the mathematics for computing the shared secret. The c		<t indent="0" pn="section-6.3.1-3.2.1">The curve selected controls
	urve selected also controls how a point in the curve is represented and what hap		not only the size of the shared secret, but the mathematics for computing the s
	pens for the identity points on the curve. In this specification, we allow for		hared secret. The curve selected also controls how a point in the curve is repr
	a number of different curves to be used. A set of curves are defined in <xref t		esented and what happens for the identity points on the curve. In this specific
	arget="x-table-ec-curves"/>.		ation, we allow for a number of different curves to be used. A set of curves is
			defined in <xref target="x-table-ec-curves" format="default" sectionFormat="of"
	</t>		derivedContent="Table 18"/>.</t>
	<t> The math used to obtain the computed secret is based on the curv		<t indent="0" pn="section-6.3.1-3.2.2"> The math used to obtain th
	e selected and not on the ECDH algorithm. For this reason, a new algorithm does		e computed secret is based on the curve selected and not on the ECDH algorithm.
	not need to be defined for each of the curves. </t>		For this reason, a new algorithm does not need to be defined for each of the cu
	</li>		rves. </t>
			</dd>
	<li>Computed Secret to Shared Secret: Once the computed secret is know		<dt pn="section-6.3.1-3.3">Computed Secret to Shared Secret:</dt>
	n, the resulting value needs to be converted to a byte string to run the KDF. T		<dd pn="section-6.3.1-3.4"> Once the computed
	he x-coordinate is used for all of the curves defined in this document. For cur		secret is known, the resulting value needs to be converted to a byte
	ves X25519 and X448, the resulting value is used directly as it is a byte string		string to run the KDF. The x-coordinate is used for all of the
	of a known length. For the P-256, P-384, and P-521 curves, the x-coordinate is		curves defined in this document. For curves X25519 and X448, the
	run through the I2OSP function defined in <xref target="RFC8017"/>, using the s		resulting value is used directly, as it is a byte string of a known
	ame computation for n as is defined in <xref target="ECDSA"/>. </li>		length. For the P-256, P-384, and P-521 curves, the x-coordinate is
			run through the Integer-to-Octet-String primitive (I2OSP) function
	<li>Ephemeral-Static or Static-Static: The key agreement process may b		defined in <xref target="RFC8017" format="default" sectionFormat="of" d
	e done using either a static or an ephemeral key for the sender's side. When us		erivedContent="RFC8017"/>,
	ing ephemeral keys, the sender <bcp14>MUST</bcp14> generate a new ephemeral key		using the same computation for n as is defined in <xref target="ECDSA"
	for every key agreement operation. The ephemeral key is placed in the 'ephemera		format="default" sectionFormat="of" derivedContent="Section 2.1"/>. </dd>
	l key' parameter and <bcp14>MUST</bcp14> be present for all algorithm identifier		<dt pn="section-6.3.1-3.5">Ephemeral-Static or Static-Static:</dt>
	s that use ephemeral keys. When using static keys, the sender <bcp14>MUST</bcp1		<dd pn="section-6.3.1-3.6"> The key agreement
	4> either generate a new random value or create a unique value.		process may be done using either a static or an ephemeral
	For the KDFs used, this means either the 'salt' parameter for HKDF (<xre		key for the sender's side. When using ephemeral keys, the
	f target="HKDF_Alg_Params"/>) or the 'PartyU nonce' parameter for the context st		sender <bcp14>MUST</bcp14> generate a new ephemeral key for
	ructure (<xref target="KDF_Context_Alg_Params"/>) <bcp14>MUST</bcp14> be present		every key agreement operation. The ephemeral key is placed
	(both can be present if desired). The value in the parameter <bcp14>MUST</bcp14		in the "ephemeral key" parameter and <bcp14>MUST</bcp14> be
	> be unique for the pair of keys being used. It is acceptable to use a global c		present for all algorithm identifiers that use ephemeral
	ounter that is incremented for every static-static operation and use the resulti		keys. When using static keys, the sender
	ng value. Care must be taken that the counter is saved to permanent storage in		<bcp14>MUST</bcp14> either generate a new random value or
	a way to avoid reuse of that counter value. When using static keys, the static k		create a unique value for use as a KDF input. For the KDFs used, this
	ey should be identified to the recipient. The static key can be identified eith		means that either
	er by providing the key ('static key') or by providing a key identifier for the		the "salt" parameter for HKDF (<xref target="HKDF_Alg_Params" format="
	static key ('static key id'). Both of these header parameters are defined in <x		default" sectionFormat="of" derivedContent="Table 9"/>) or the "PartyU nonce" pa
	ref target="x-table-ecdh-es-parameter-table"/>.		rameter
	</li>		for the context structure (<xref target="KDF_Context_Alg_Params" forma
			t="default" sectionFormat="of" derivedContent="Table 10"/>) <bcp14>MUST</bcp14>
	<li>Key Derivation Algorithm: The result of an ECDH key agreement proc		be
	ess does not provide a uniformly random secret. As such, it needs to be run thr		present (both can be present if desired). The value in the
	ough a KDF in order to produce a usable key. Processing the secret through a KD		parameter <bcp14>MUST</bcp14> be unique for the pair of keys
	F also allows for the introduction of context material: how the key is going to		being used. It is acceptable to use a global counter that
	be used and one-time material for static-static key agreement. All of the algor		is incremented for every Static-Static operation and use the
	ithms defined in this document use one of the HKDF algorithms defined in <xref t		resulting value. Care must be taken that the counter is
	arget="HKDF-section"/> with the context structure defined in <xref target="conte		saved to permanent storage in a way that avoids reuse of that
	xt"/>. </li>		counter value. When using static keys, the static key should
			be identified to the recipient. The static key can be
	<li>Key Wrap Algorithm: No key wrap algorithm is used. This is repres		identified by providing either the key ("static key") or
	ented in <xref target="x-table-ecdh-es-table"/> as 'none'. The key size for the		a key identifier for the static key ("static key
	context structure is the content layer encryption algorithm size. </li>		id"). Both of these header parameters are defined in <xref target="x-
	</ul>		table-ecdh-es-parameter-table" format="default" sectionFormat="of" derivedConten
	<t>		t="Table 15"/>.
			</dd>
			<dt pn="section-6.3.1-3.7">Key Derivation Algorithm:</dt>
			<dd pn="section-6.3.1-3.8">The result of an ECDH
			key agreement process does not provide a uniformly random secret.
			As such, it needs to be run through a KDF in order to produce a usable
			key. Processing the secret through a KDF also allows for the
			introduction of context material: how the key is going to be used
			and one-time material for Static-Static key agreement. All of the
			algorithms defined in this document use one of the HKDF algorithms
			defined in <xref target="HKDF-section" format="default" sectionFormat="
			of" derivedContent="Section 5.1"/> with the context structure
			defined in <xref target="context" format="default" sectionFormat="of" d
			erivedContent="Section 5.2"/>. </dd>
			<dt pn="section-6.3.1-3.9">Key Wrap Algorithm:</dt>
			<dd pn="section-6.3.1-3.10"> No key wrap algorithm is used.
			This is represented in <xref target="x-table-ecdh-es-table" format="def
			ault" sectionFormat="of" derivedContent="Table 14"/> as
			"none". The key size for the context structure is the
			content layer encryption algorithm size. </dd>
			</dl>
			<t indent="0" pn="section-6.3.1-4">
	COSE does not have an Ephemeral-Ephemeral version defined.		COSE does not have an Ephemeral-Ephemeral version defined.
	The reason for this is that COSE is not an online protocol by itself a		The reason for this is that COSE is not an online protocol by itself a
	nd thus does not have a method to establish ephemeral secrets on both sides.		nd thus does not have a method of establishing ephemeral secrets on both sides.
	The expectation is that a protocol would establish the secrets for bot		The expectation is that a protocol would establish the secrets for bot
	h sides, and then they would be used as static-static for the purposes of COSE,		h sides, and then they would be used as Static-Static for the purposes of COSE,
	or that the protocol would generate a shared secret and a direct encryption woul		or that the protocol would generate a shared secret and a direct encryption woul
	d be used.		d be used.
	</t>
	<t>The set of direct ECDH algorithms defined in this document are found
	in <xref target="x-table-ecdh-es-table"/>. </t>
	<table anchor="x-table-ecdh-es-table" align="center">
	<name>ECDH Algorithm Values</name>
	<thead>
	<tr>
	<th>Name</th>
	<th>Value</th>
	<th>KDF</th>
	<th>Ephemeral- Static</th>
	<th>Key Wrap</th>
	<th>Description</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td>ECDH-ES + HKDF-256</td>
	<td>-25</td>
	<td>HKDF - SHA-256</td>
	<td>yes</td>
	<td>none</td>
	<td>ECDH ES w/ HKDF - generate key directly</td>
	</tr>
	<tr>
	<td>ECDH-ES + HKDF-512</td>
	<td>-26</td>
	<td>HKDF - SHA-512</td>
	<td>yes</td>
	<td>none</td>
	<td>ECDH ES w/ HKDF - generate key directly</td>
	</tr>
	<tr>
	<td>ECDH-SS + HKDF-256</td>
	<td>-27</td>
	<td>HKDF - SHA-256</td>
	<td>no</td>
	<td>none</td>
	<td>ECDH SS w/ HKDF - generate key directly</td>
	</tr>
	<tr>
	<td>ECDH-SS + HKDF-512</td>
	<td>-28</td>
	<td>HKDF - SHA-512</td>
	<td>no</td>
	<td>none</td>
	<td>ECDH SS w/ HKDF - generate key directly</td>
	</tr>
	</tbody>
	</table>
	<table anchor="x-table-ecdh-es-parameter-table" align="center">
	<name>ECDH Algorithm Parameters</name>
	<thead>
	<tr>
	<th>Name</th>
	<th>Label</th>
	<th>Type</th>
	<th>Algorithm</th>
	<th>Description</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td>ephemeral key</td>
	<td>-1</td>
	<td>COSE_Key</td>
	<td>ECDH-ES+HKDF-256, ECDH-ES+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A1
	92KW, ECDH-ES+A256KW</td>
	<td>Ephemeral public key for the sender</td>
	</tr>
	<tr>
	<td>static key</td>
	<td>-2</td>
	<td>COSE_Key</td>
	<td>ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-SS+A128KW, ECDH-SS+A1
	92KW, ECDH-SS+A256KW </td>
	<td>Static public key for the sender</td>
	</tr>
	<tr>
	<td>static key id </td>
	<td>-3</td>
	<td>bstr</td>
	<td>ECDH-SS+HKDF-256, ECDH-SS+HKDF-512, ECDH-SS+A128KW, ECDH-SS+A1
	92KW, ECDH-SS+A256KW </td>
	<td>Static public key identifier for the sender</td>
	</tr>
	</tbody>
	</table>
	<t>This document defines these algorithms to be used with the curves P-2
	56, P-384, P-521, X25519, and X448. Implementations <bcp14>MUST</bcp14> verify
	that the key type and curve are correct. Different curves are restricted to dif
	ferent key types. Implementations <bcp14>MUST</bcp14> verify that the curve and
	algorithm are appropriate for the entities involved. </t>
	<t>When using a COSE key for this algorithm, the following checks are ma
	de:
	</t>
	<ul>
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST
	</bcp14> be 'EC2' or 'OKP'.</li>
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the ke
	y agreement algorithm being used.</li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include
	'derive key' or 'derive bits' for the private key.</li>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> be empty
	for the public key.</li>
	</ul>
	<section>
	<name>Security Considerations for ECDH</name>
	<t>
	There is a method of checking that points provided from external ent
	ities are valid.
	For the 'EC2' key format, this can be done by checking that the x an
	d y values form a point on the curve.
	For the 'OKP' format, there is no simple way to do point validation.
	</t>		</t>
	<t>		<t indent="0" pn="section-6.3.1-5">The set of direct ECDH algorithms d
	Consideration was given to requiring that the public keys of both en		efined in this document is found
	tities be provided as part of the key derivation process (as recommended in <rel		in <xref target="x-table-ecdh-es-table" format="default" sectionFormat="o
	ref target="RFC7748" section="6.4"/>).		f" derivedContent="Table 14"/>. </t>
	This was not done as COSE is used in a store and forward format rath		<table anchor="x-table-ecdh-es-table" align="center" pn="table-14">
	er than in online key exchange.		<name slugifiedName="name-ecdh-algorithm-values">ECDH Algorithm Valu
			es</name>
			<thead>
			<tr>
			<th align="left" colspan="1" rowspan="1">Name</th>
			<th align="left" colspan="1" rowspan="1">Value</th>
			<th align="left" colspan="1" rowspan="1">KDF</th>
			<th align="left" colspan="1" rowspan="1">Ephemeral-Static</th>
			<th align="left" colspan="1" rowspan="1">Key Wrap</th>
			<th align="left" colspan="1" rowspan="1">Description</th>
			</tr>
			</thead>
			<tbody>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-ES + HKDF-256</td>
			<td align="left" colspan="1" rowspan="1">-25</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-256</td>
			<td align="left" colspan="1" rowspan="1">yes</td>
			<td align="left" colspan="1" rowspan="1">none</td>
			<td align="left" colspan="1" rowspan="1">ECDH ES w/ HKDF -- gene
			rate key directly</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-ES + HKDF-512</td>
			<td align="left" colspan="1" rowspan="1">-26</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-512</td>
			<td align="left" colspan="1" rowspan="1">yes</td>
			<td align="left" colspan="1" rowspan="1">none</td>
			<td align="left" colspan="1" rowspan="1">ECDH ES w/ HKDF -- gene
			rate key directly</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-SS + HKDF-256</td>
			<td align="left" colspan="1" rowspan="1">-27</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-256</td>
			<td align="left" colspan="1" rowspan="1">no</td>
			<td align="left" colspan="1" rowspan="1">none</td>
			<td align="left" colspan="1" rowspan="1">ECDH SS w/ HKDF -- gene
			rate key directly</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-SS + HKDF-512</td>
			<td align="left" colspan="1" rowspan="1">-28</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-512</td>
			<td align="left" colspan="1" rowspan="1">no</td>
			<td align="left" colspan="1" rowspan="1">none</td>
			<td align="left" colspan="1" rowspan="1">ECDH SS w/ HKDF -- gene
			rate key directly</td>
			</tr>
			</tbody>
			</table>
			<table anchor="x-table-ecdh-es-parameter-table" align="center" pn="tab
			le-15">
			<name slugifiedName="name-ecdh-algorithm-parameters">ECDH Algorithm
			Parameters</name>
			<thead>
			<tr>
			<th align="left" colspan="1" rowspan="1">Name</th>
			<th align="left" colspan="1" rowspan="1">Label</th>
			<th align="left" colspan="1" rowspan="1">Type</th>
			<th align="left" colspan="1" rowspan="1">Algorithm</th>
			<th align="left" colspan="1" rowspan="1">Description</th>
			</tr>
			</thead>
			<tbody>
			<tr>
			<td align="left" colspan="1" rowspan="1">ephemeral key</td>
			<td align="left" colspan="1" rowspan="1">-1</td>
			<td align="left" colspan="1" rowspan="1">COSE_Key</td>
			<td align="left" colspan="1" rowspan="1">ECDH-ES+HKDF-256, ECDH-
			ES+HKDF-512, ECDH-ES+A128KW, ECDH-ES+A192KW, ECDH-ES+A256KW</td>
			<td align="left" colspan="1" rowspan="1">Ephemeral public key fo
			r the sender</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">static key</td>
			<td align="left" colspan="1" rowspan="1">-2</td>
			<td align="left" colspan="1" rowspan="1">COSE_Key</td>
			<td align="left" colspan="1" rowspan="1">ECDH-SS+HKDF-256, ECDH-
			SS+HKDF-512, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
			<td align="left" colspan="1" rowspan="1">Static public key for t
			he sender</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">static key id </td>
			<td align="left" colspan="1" rowspan="1">-3</td>
			<td align="left" colspan="1" rowspan="1">bstr</td>
			<td align="left" colspan="1" rowspan="1">ECDH-SS+HKDF-256, ECDH-
			SS+HKDF-512, ECDH-SS+A128KW, ECDH-SS+A192KW, ECDH-SS+A256KW </td>
			<td align="left" colspan="1" rowspan="1">Static public key ident
			ifier for the sender</td>
			</tr>
			</tbody>
			</table>
			<t indent="0" pn="section-6.3.1-8">This document defines these algorit
			hms to be used with the curves P-256, P-384, P-521, X25519, and X448. Implement
			ations <bcp14>MUST</bcp14> verify that the key type and curve are correct. Diff
			erent curves are restricted to different key types. Implementations <bcp14>MUST
			</bcp14> verify that the curve and algorithm are appropriate for the entities in
			volved. </t>
			<t indent="0" pn="section-6.3.1-9">When using a COSE key for this algo
			rithm, the following checks are made:
			</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section
			-6.3.1-10">
			<li pn="section-6.3.1-10.1">The "kty" field <bcp14>MUST</bcp14> be p
			resent, and it <bcp14>MUST</bcp14> be "EC2" or "OKP".</li>
			<li pn="section-6.3.1-10.2">If the "alg" field is present, it <bcp14
			>MUST</bcp14> match the
			key agreement algorithm being used.</li>
			<li pn="section-6.3.1-10.3">If the "key_ops" field is present, it <b
			cp14>MUST</bcp14> include "derive key" or "derive bits" for the private key.</li
			>
			<li pn="section-6.3.1-10.4">If the "key_ops" field is present, it <b
			cp14>MUST</bcp14> be empty for the public key.</li>
			</ul>
			<section numbered="true" removeInRFC="false" toc="exclude" pn="section
			-6.3.1.1">
			<name slugifiedName="name-security-considerations-for-e">Security Co
			nsiderations for ECDH</name>
			<t indent="0" pn="section-6.3.1.1-1">
			There is a method of checking that points provided from external ent
			ities are valid.
			For the "EC2" key format, this can be done by checking that the x an
			d y values form a point on the curve.
			For the "OKP" format, there is no simple way to perform point valida
			tion.
			</t>
			<t indent="0" pn="section-6.3.1.1-2">
			Consideration was given to requiring that the public keys of both
			entities be provided as part of the key derivation process (as
			recommended in <xref target="RFC7748" section="6.1" sectionFormat="of
			" format="default" derivedLink="https://rfc-editor.org/rfc/rfc7748#section-6.1"
			derivedContent="RFC7748"/>). This was
			not done, because COSE is used in a store-and-forward
			format rather than in online key exchange.
	In order for this to be a problem, either the receiver public key ha s to be chosen maliciously or the sender has to be malicious.		In order for this to be a problem, either the receiver public key ha s to be chosen maliciously or the sender has to be malicious.
	In either case, all security evaporates anyway.		In either case, all security evaporates anyway.
	</t>		</t>
	<t>A proof of possession of the private key associated with the public		<t indent="0" pn="section-6.3.1.1-3">A proof of possession of the pr
	key is recommended when a key is moved from untrusted to trusted (either by the		ivate key associated with the public key is recommended when a key is moved from
	end user or by the entity that is responsible for making trust statements on ke		untrusted to trusted (either by the end user or by the entity that is responsib
	ys). </t>		le for making trust statements on keys). </t>
			</section>
	</section>		</section>
	</section>		</section>
	</section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-6.4
	<section>		">
	<name>Key Agreement with Key Wrap</name>		<name slugifiedName="name-key-agreement-with-key-wrap">Key Agreement wit
	<t>		h Key Wrap</name>
	Key Agreement with Key Wrap is defined in <relref section="9.5.5" targ		<t indent="0" pn="section-6.4-1">
	et="I-D.ietf-cose-rfc8152bis-struct"/>.		Key Agreement with Key Wrap is defined in <xref section="8.5.5" target
	Information about how to fill in the COSE_Recipient structure are deta		="RFC9052" sectionFormat="of" format="default" derivedLink="https://rfc-editor.o
	iled there.		rg/rfc/rfc9052#section-8.5.5" derivedContent="RFC9052"/>.
	</t>		Information about how to fill in the COSE_Recipient structure is detai
			led there.
	<section anchor="ECDH-wrap">
	<name>ECDH with Key Wrap</name>
	<t>These algorithms are defined in <xref target="x-table-ecdh-es-table-w
	rap"/>. </t>
	<t>ECDH with Key Agreement is parameterized by the same header parameter
	s as for ECDH; see <xref target="ECDH"/>, with the following modifications:
	</t>
	<ul>
	<li>Key Wrap Algorithm: Any of the key wrap algorithms defined in <xre
	f target="key_wrap_algs"/> are supported. The size of the key used for the key
	wrap algorithm is fed into the KDF. The set of identifiers are found in <xref t
	arget="x-table-ecdh-es-table-wrap"/>. </li>
	</ul>
	<table anchor="x-table-ecdh-es-table-wrap" align="center">
	<name>ECDH Algorithm Values with Key Wrap</name>
	<thead>
	<tr>
	<th>Name</th>
	<th>Value</th>
	<th>KDF</th>
	<th>Ephemeral- Static</th>
	<th>Key Wrap</th>
	<th>Description</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td>ECDH-ES + A128KW</td>
	<td>-29</td>
	<td>HKDF - SHA-256</td>
	<td>yes</td>
	<td>A128KW</td>
	<td>ECDH ES w/ Concat KDF and AES Key Wrap w/ 128-bit key</td>
	</tr>
	<tr>
	<td>ECDH-ES + A192KW</td>
	<td>-30</td>
	<td>HKDF - SHA-256</td>
	<td>yes</td>
	<td>A192KW</td>
	<td>ECDH ES w/ Concat KDF and AES Key Wrap w/ 192-bit key</td>
	</tr>
	<tr>
	<td>ECDH-ES + A256KW</td>
	<td>-31</td>
	<td>HKDF - SHA-256</td>
	<td>yes</td>
	<td>A256KW</td>
	<td>ECDH ES w/ Concat KDF and AES Key Wrap w/ 256-bit key</td>
	</tr>
	<tr>
	<td>ECDH-SS + A128KW</td>
	<td>-32</td>
	<td>HKDF - SHA-256</td>
	<td>no</td>
	<td>A128KW</td>
	<td>ECDH SS w/ Concat KDF and AES Key Wrap w/ 128-bit key</td>
	</tr>
	<tr>
	<td>ECDH-SS + A192KW</td>
	<td>-33</td>
	<td>HKDF - SHA-256</td>
	<td>no</td>
	<td>A192KW</td>
	<td>ECDH SS w/ Concat KDF and AES Key Wrap w/ 192-bit key</td>
	</tr>
	<tr>
	<td>ECDH-SS + A256KW</td>
	<td>-34</td>
	<td>HKDF - SHA-256</td>
	<td>no</td>
	<td>A256KW</td>
	<td>ECDH SS w/ Concat KDF and AES Key Wrap w/ 256-bit key</td>
	</tr>
	</tbody>
	</table>
	<t>When using a COSE key for this algorithm, the following checks are ma
	de:
	</t>		</t>
			<section anchor="ECDH-wrap" numbered="true" removeInRFC="false" toc="inc
	<ul>		lude" pn="section-6.4.1">
			<name slugifiedName="name-ecdh-with-key-wrap">ECDH with Key Wrap</name
	<li>The 'kty' field <bcp14>MUST</bcp14> be present, and it <bcp14>MUST		>
	</bcp14> be 'EC2' or 'OKP'.</li>		<t indent="0" pn="section-6.4.1-1">These algorithms are defined in <xr
			ef target="x-table-ecdh-es-table-wrap" format="default" sectionFormat="of" deriv
	<li>If the 'alg' field is present, it <bcp14>MUST</bcp14> match the ke		edContent="Table 16"/>. </t>
	y agreement algorithm being used.</li>		<t indent="0" pn="section-6.4.1-2">ECDH with Key Agreement is paramete
			rized by the same header parameters as for ECDH; see <xref target="ECDH" format=
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> include		"default" sectionFormat="of" derivedContent="Section 6.3.1"/>, with the followin
	'derive key' or 'derive bits' for the private key.</li>		g modifications:
			</t>
	<li>If the 'key_ops' field is present, it <bcp14>MUST</bcp14> be empty		<dl indent="3" newline="false" spacing="normal" pn="section-6.4.1-3">
	for the public key.</li>		<dt pn="section-6.4.1-3.1">Key Wrap Algorithm:</dt>
	</ul>		<dd pn="section-6.4.1-3.2"> Any of the key wrap algorithms
			defined in <xref target="key_wrap_algs" format="default" sectionFormat=
			"of" derivedContent="Section 6.2"/> are supported. The size
			of the key used for the key wrap algorithm is fed into the KDF. The
			set of identifiers is found in <xref target="x-table-ecdh-es-table-wrap
			" format="default" sectionFormat="of" derivedContent="Table 16"/>. </dd>
			</dl>
			<table anchor="x-table-ecdh-es-table-wrap" align="center" pn="table-16
			">
			<name slugifiedName="name-ecdh-algorithm-values-with-">ECDH Algorith
			m Values with Key Wrap</name>
			<thead>
			<tr>
			<th align="left" colspan="1" rowspan="1">Name</th>
			<th align="left" colspan="1" rowspan="1">Value</th>
			<th align="left" colspan="1" rowspan="1">KDF</th>
			<th align="left" colspan="1" rowspan="1">Ephemeral-Static</th>
			<th align="left" colspan="1" rowspan="1">Key Wrap</th>
			<th align="left" colspan="1" rowspan="1">Description</th>
			</tr>
			</thead>
			<tbody>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-ES + A128KW</td>
			<td align="left" colspan="1" rowspan="1">-29</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-256</td>
			<td align="left" colspan="1" rowspan="1">yes</td>
			<td align="left" colspan="1" rowspan="1">A128KW</td>
			<td align="left" colspan="1" rowspan="1">ECDH ES w/ HKDF and AES
			Key Wrap w/ 128-bit key</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-ES + A192KW</td>
			<td align="left" colspan="1" rowspan="1">-30</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-256</td>
			<td align="left" colspan="1" rowspan="1">yes</td>
			<td align="left" colspan="1" rowspan="1">A192KW</td>
			<td align="left" colspan="1" rowspan="1">ECDH ES w/ HKDF and AES
			Key Wrap w/ 192-bit key</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-ES + A256KW</td>
			<td align="left" colspan="1" rowspan="1">-31</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-256</td>
			<td align="left" colspan="1" rowspan="1">yes</td>
			<td align="left" colspan="1" rowspan="1">A256KW</td>
			<td align="left" colspan="1" rowspan="1">ECDH ES w/ HKDF and AES
			Key Wrap w/ 256-bit key</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-SS + A128KW</td>
			<td align="left" colspan="1" rowspan="1">-32</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-256</td>
			<td align="left" colspan="1" rowspan="1">no</td>
			<td align="left" colspan="1" rowspan="1">A128KW</td>
			<td align="left" colspan="1" rowspan="1">ECDH SS w/ HKDF and AES
			Key Wrap w/ 128-bit key</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-SS + A192KW</td>
			<td align="left" colspan="1" rowspan="1">-33</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-256</td>
			<td align="left" colspan="1" rowspan="1">no</td>
			<td align="left" colspan="1" rowspan="1">A192KW</td>
			<td align="left" colspan="1" rowspan="1">ECDH SS w/ HKDF and AES
			Key Wrap w/ 192-bit key</td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">ECDH-SS + A256KW</td>
			<td align="left" colspan="1" rowspan="1">-34</td>
			<td align="left" colspan="1" rowspan="1">HKDF -- SHA-256</td>
			<td align="left" colspan="1" rowspan="1">no</td>
			<td align="left" colspan="1" rowspan="1">A256KW</td>
			<td align="left" colspan="1" rowspan="1">ECDH SS w/ HKDF and AES
			Key Wrap w/ 256-bit key</td>
			</tr>
			</tbody>
			</table>
			<t indent="0" pn="section-6.4.1-5">When using a COSE key for this algo
			rithm, the following checks are made:
			</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section
			-6.4.1-6">
			<li pn="section-6.4.1-6.1">The "kty" field <bcp14>MUST</bcp14> be pr
			esent, and it <bcp14>MUST</bcp14> be "EC2" or "OKP".</li>
			<li pn="section-6.4.1-6.2">If the "alg" field is present, it <bcp14>
			MUST</bcp14> match the key agreement algorithm being used.</li>
			<li pn="section-6.4.1-6.3">If the "key_ops" field is present, it <bc
			p14>MUST</bcp14> include "derive key" or "derive bits" for the private key.</li>
			<li pn="section-6.4.1-6.4">If the "key_ops" field is present, it <bc
			p14>MUST</bcp14> be empty for the public key.</li>
			</ul>
			</section>
	</section>		</section>
	</section>		</section>
	</section>		<section anchor="Key-specific-labels" numbered="true" removeInRFC="false" to
	<section anchor="Key-specific-labels">		c="include" pn="section-7">
			<name slugifiedName="name-key-object-parameters">Key Object Parameters</na
	<name>Key Object Parameters</name>		me>
	<t>The COSE_Key object defines a way to hold a single key object. It is s		<t indent="0" pn="section-7-1">The COSE_Key object defines a way to hold a
	till required that the members of individual key types be defined. This section		single key object. It is still required that the members of individual key typ
	of the document is where we define an initial set of members for specific key t		es be defined. This section of the document is where we define an initial set o
	ypes. </t>		f members for specific key types. </t>
	<t>For each of the key types, we define both public and private members.		<t indent="0" pn="section-7-2">For each of the key types, we define both p
	The public members are what is transmitted to others for their usage. Private m		ublic and private members.
	embers allow for the archival of keys by individuals. However, there are some c		The public members are what is transmitted to others for their usage.
	ircumstances in which private keys may be distributed to entities in a protocol.		Private members allow individuals to archive keys. However,
	Examples include: entities that have poor random number generation, centraliz		there are some circumstances in which private keys may be distributed to
	ed key creation for multi-cast type operations, and protocols in which a shared		entities in a protocol. Examples include: entities that have poor
	secret is used as a bearer token for authorization purposes. </t>		random number generation, centralized key creation for multicast-type
	<t>Key types are identified by the 'kty' member of the COSE_Key object. I		operations, and protocols in which a shared secret is used as a bearer
	n this document, we define four values for the member: </t>		token for authorization purposes. </t>
	<table anchor="x-table_key_types" align="center">		<t indent="0" pn="section-7-3">Key types are identified by the "kty" membe
			r of the COSE_Key object. In this document, we define four values for the membe
	<name>Key Type Values</name>		r: </t>
			<table anchor="x-table_key_types" align="center" pn="table-17">
			<name slugifiedName="name-key-type-values">Key Type Values</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>OKP</td>		<td align="left" colspan="1" rowspan="1">OKP</td>
	<td>1</td>		<td align="center" colspan="1" rowspan="1">1</td>
	<td>Octet Key Pair</td>		<td align="left" colspan="1" rowspan="1">Octet Key Pair</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>EC2</td>		<td align="left" colspan="1" rowspan="1">EC2</td>
	<td>2</td>		<td align="center" colspan="1" rowspan="1">2</td>
	<td>Elliptic Curve Keys w/ x- and y-coordinate pair</td>		<td align="left" colspan="1" rowspan="1">Elliptic Curve Keys w/ x- a
			nd y-coordinate pair</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>Symmetric</td>		<td align="left" colspan="1" rowspan="1">Symmetric</td>
	<td>4</td>		<td align="center" colspan="1" rowspan="1">4</td>
	<td>Symmetric Keys</td>		<td align="left" colspan="1" rowspan="1">Symmetric Keys</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>Reserved</td>		<td align="left" colspan="1" rowspan="1">Reserved</td>
	<td>0</td>		<td align="center" colspan="1" rowspan="1">0</td>
	<td>This value is reserved</td>		<td align="left" colspan="1" rowspan="1">This value is reserved</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-7.1
			">
	<name>Elliptic Curve Keys</name>		<name slugifiedName="name-elliptic-curve-keys">Elliptic Curve Keys</name
	<t>Two different key structures are defined for elliptic curve keys. On		>
	e version uses both an x-coordinate and a y-coordinate, potentially with point c		<t indent="0" pn="section-7.1-1">Two different key structures are define
	ompression ('EC2'). This is the traditional EC point representation that is use		d for elliptic curve keys.
	d in <xref target="RFC5480"/>. The other version uses only the x-coordinate as		One version uses both an x-coordinate and a y-coordinate, potentially
	the y-coordinate is either to be recomputed or not needed for the key agreement		with point compression ("EC2"). This is the conventional
	operation ('OKP'). </t>		elliptic curve (EC) point
	<t>Applications <bcp14>MUST</bcp14> check that the curve and the key typ		representation that is used in <xref target="RFC5480" format="default" se
	e are consistent and reject a key if they are not. </t>		ctionFormat="of" derivedContent="RFC5480"/>. The other
	<table anchor="x-table-ec-curves" align="center">		version uses only the x-coordinate, as the y-coordinate is either to
			be recomputed or not needed for the key agreement operation ("OKP").
	<name>Elliptic Curves</name>		</t>
			<t indent="0" pn="section-7.1-2">Applications <bcp14>MUST</bcp14> check
			that the curve and the key type are consistent and reject a key if they are not.
			</t>
			<table anchor="x-table-ec-curves" align="center" pn="table-18">
			<name slugifiedName="name-elliptic-curves">Elliptic Curves</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="center" colspan="1" rowspan="1">Value</th>
	<th>Key Type</th>		<th align="center" colspan="1" rowspan="1">Key Type</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>P-256</td>		<td align="left" colspan="1" rowspan="1">P-256</td>
	<td>1</td>		<td align="center" colspan="1" rowspan="1">1</td>
	<td>EC2</td>		<td align="center" colspan="1" rowspan="1">EC2</td>
	<td>NIST P-256 also known as secp256r1</td>		<td align="left" colspan="1" rowspan="1">NIST P-256, also known as
			secp256r1</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>P-384</td>		<td align="left" colspan="1" rowspan="1">P-384</td>
	<td>2</td>		<td align="center" colspan="1" rowspan="1">2</td>
	<td>EC2</td>		<td align="center" colspan="1" rowspan="1">EC2</td>
	<td>NIST P-384 also known as secp384r1</td>		<td align="left" colspan="1" rowspan="1">NIST P-384, also known as
			secp384r1</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>P-521</td>		<td align="left" colspan="1" rowspan="1">P-521</td>
	<td>3</td>		<td align="center" colspan="1" rowspan="1">3</td>
	<td>EC2</td>		<td align="center" colspan="1" rowspan="1">EC2</td>
	<td>NIST P-521 also known as secp521r1</td>		<td align="left" colspan="1" rowspan="1">NIST P-521, also known as
			secp521r1</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>X25519</td>		<td align="left" colspan="1" rowspan="1">X25519</td>
	<td>4</td>		<td align="center" colspan="1" rowspan="1">4</td>
	<td>OKP</td>		<td align="center" colspan="1" rowspan="1">OKP</td>
	<td>X25519 for use w/ ECDH only</td>		<td align="left" colspan="1" rowspan="1">X25519 for use w/ ECDH on
			ly</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>X448</td>		<td align="left" colspan="1" rowspan="1">X448</td>
	<td>5</td>		<td align="center" colspan="1" rowspan="1">5</td>
	<td>OKP</td>		<td align="center" colspan="1" rowspan="1">OKP</td>
	<td>X448 for use w/ ECDH only</td>		<td align="left" colspan="1" rowspan="1">X448 for use w/ ECDH only
			</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>Ed25519</td>		<td align="left" colspan="1" rowspan="1">Ed25519</td>
	<td>6</td>		<td align="center" colspan="1" rowspan="1">6</td>
	<td>OKP</td>		<td align="center" colspan="1" rowspan="1">OKP</td>
	<td>Ed25519 for use w/ EdDSA only</td>		<td align="left" colspan="1" rowspan="1">Ed25519 for use w/ EdDSA
			only</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>Ed448</td>		<td align="left" colspan="1" rowspan="1">Ed448</td>
	<td>7</td>		<td align="center" colspan="1" rowspan="1">7</td>
	<td>OKP</td>		<td align="center" colspan="1" rowspan="1">OKP</td>
	<td>Ed448 for use w/ EdDSA only</td>		<td align="left" colspan="1" rowspan="1">Ed448 for use w/ EdDSA on
			ly</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<section anchor="EC2-Keys">		<section anchor="EC2-Keys" numbered="true" removeInRFC="false" toc="incl
			ude" pn="section-7.1.1">
	<name>Double Coordinate Curves</name>		<name slugifiedName="name-double-coordinate-curves">Double Coordinate
	<t>The traditional way of sending ECs has been to send either both the		Curves</name>
	x-coordinate and y-coordinate or the x-coordinate and a sign bit for the y-coor		<t indent="0" pn="section-7.1.1-1">Generally, protocols transmit ellip
	dinate. The latter encoding has not been recommended in the IETF due to potenti		tic-curve points as either the
	al IPR issues. However, for operations in constrained environments, the ability		x-coordinate and y-coordinate or the x-coordinate and a sign bit
	to shrink a message by not sending the y-coordinate is potentially useful. </t		for the y-coordinate. The latter encoding has not been recommended
	>		by the IETF due to potential IPR
	<t>For EC keys with both coordinates, the 'kty' member is set to 2 (EC		issues. However, for operations in constrained environments, the
	2). The key parameters defined in this section are summarized in <xref target="		ability to shrink a message by not sending the y-coordinate is
	x-table-ec2-keys"/>. The members that are defined for this key type are:		potentially useful. </t>
			<t indent="0" pn="section-7.1.1-2">For EC keys with both coordinates,
			the "kty" member is set to 2 (EC2). The key parameters defined in this section
			are summarized in <xref target="x-table-ec2-keys" format="default" sectionFormat
			="of" derivedContent="Table 19"/>. The members that are defined for this key ty
			pe are:
	</t>		</t>
			<dl newline="false" indent="6" spacing="normal" pn="section-7.1.1-3">
	<dl newline="false" indent="5">		<dt pn="section-7.1.1-3.1">crv:</dt>
	<dt>crv:</dt>		<dd pn="section-7.1.1-3.2">This contains an identifier of the curve
			to be used with the key. The curves defined in this document for this key type c
	<dd>This contains an identifier of the curve to be used with the key		an be found in <xref target="x-table-ec-curves" format="default" sectionFormat="
	. The curves defined in this document for this key type can be found in <xref ta		of" derivedContent="Table 18"/>. Other curves may be registered in the future,
	rget="x-table-ec-curves"/>. Other curves may be registered in the future, and p		and private curves can be used as well. </dd>
	rivate curves can be used as well. </dd>		<dt pn="section-7.1.1-3.3">x:</dt>
	<dt>x:</dt>		<dd pn="section-7.1.1-3.4">This contains the x-coordinate for the EC
			point. The integer
	<dd>This contains the x-coordinate for the EC point. The integer is		is converted to a byte string as defined in <xref target="SEC1" forma
	converted to a byte string as defined in <xref target="SEC1"/>. Leading zero o		t="default" sectionFormat="of" derivedContent="SEC1"/>.
	ctets <bcp14>MUST</bcp14> be preserved.		Leading-zero octets <bcp14>MUST</bcp14> be preserved.
	</dd>		</dd>
	<dt>y:</dt>		<dt pn="section-7.1.1-3.5">y:</dt>
			<dd pn="section-7.1.1-3.6">This contains either the sign bit or the
	<dd>This contains either the sign bit or the value of the y-coordina		value of the y-coordinate for the EC point. When encoding the value y, the inte
	te for the EC point. When encoding the value y, the integer is converted to an		ger is converted to a byte string (as defined in <xref target="SEC1" format="def
	byte string (as defined in <xref target="SEC1"/>) and encoded as a CBOR bstr. L		ault" sectionFormat="of" derivedContent="SEC1"/>) and encoded as a CBOR bstr. L
	eading zero octets <bcp14>MUST</bcp14> be preserved. The compressed point encod		eading-zero octets <bcp14>MUST</bcp14> be preserved. Compressed point encoding
	ing is also supported. Compute the sign bit as laid out in the Elliptic-Curve-P		is also supported. Compute the sign bit as laid out in the Elliptic-Curve-Point
	oint-to-Octet-String Conversion function of <xref target="SEC1"/>. If the sign		-to-Octet-String Conversion function of <xref target="SEC1" format="default" sec
	bit is zero, then encode y as a CBOR false value; otherwise, encode y as a CBOR		tionFormat="of" derivedContent="SEC1"/>. If the sign bit is zero, then encode y
	true value. The encoding of the infinity point is not supported. </dd>		as a CBOR false value; otherwise, encode y as a CBOR true value. The encoding
	<dt>d:</dt>		of the infinity point is not supported. </dd>
			<dt pn="section-7.1.1-3.7">d:</dt>
	<dd>This contains the private key. </dd>		<dd pn="section-7.1.1-3.8">This contains the private key. </dd>
	</dl>		</dl>
	<t>For public keys, it is <bcp14>REQUIRED</bcp14> that 'crv', 'x', and		<t indent="0" pn="section-7.1.1-4">For public keys, it is <bcp14>REQUI
	'y' be present in the structure. For private keys, it is <bcp14>REQUIRED</bcp1		RED</bcp14> that "crv", "x", and "y" be present in the structure. For private k
	4> that 'crv' and 'd' be present in the structure. For private keys, it is <bcp		eys, it is <bcp14>REQUIRED</bcp14> that "crv" and "d" be present in the structur
	14>RECOMMENDED</bcp14> that 'x' and 'y' also be present, but they can be recompu		e. For private keys, it is <bcp14>RECOMMENDED</bcp14> that "x" and "y" also be
	ted from the required elements and omitting them saves on space. </t>		present, but they can be recomputed from the required elements, and omitting the
	<table anchor="x-table-ec2-keys" align="center">		m saves on space. </t>
			<table anchor="x-table-ec2-keys" align="center" pn="table-19">
	<name>EC Key Parameters</name>		<name slugifiedName="name-ec-key-parameters">EC Key Parameters</name
			>
	<thead>		<thead>
	<tr>		<tr>
	<th>Key Type</th>		<th align="center" colspan="1" rowspan="1">Key Type</th>
	<th>Name</th>		<th align="center" colspan="1" rowspan="1">Name</th>
	<th>Label</th>		<th align="center" colspan="1" rowspan="1">Label</th>
	<th>CBOR Type</th>		<th align="left" colspan="1" rowspan="1">CBOR Type</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>2</td>		<td align="center" colspan="1" rowspan="1">2</td>
	<td>crv</td>		<td align="center" colspan="1" rowspan="1">crv</td>
	<td>-1</td>		<td align="center" colspan="1" rowspan="1">-1</td>
	<td>int / tstr</td>		<td align="left" colspan="1" rowspan="1">int / tstr</td>
	<td>EC identifier - Taken from the "COSE Elliptic Curves" regist		<td align="left" colspan="1" rowspan="1">EC identifier -- Taken
	ry</td>		from the "COSE Elliptic Curves" registry</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>2</td>		<td align="center" colspan="1" rowspan="1">2</td>
	<td>x</td>		<td align="center" colspan="1" rowspan="1">x</td>
	<td>-2</td>		<td align="center" colspan="1" rowspan="1">-2</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>x-coordinate</td>		<td align="left" colspan="1" rowspan="1">x-coordinate</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>2</td>		<td align="center" colspan="1" rowspan="1">2</td>
	<td>y</td>		<td align="center" colspan="1" rowspan="1">y</td>
	<td>-3</td>		<td align="center" colspan="1" rowspan="1">-3</td>
	<td>bstr / bool</td>		<td align="left" colspan="1" rowspan="1">bstr / bool</td>
	<td>y-coordinate</td>		<td align="left" colspan="1" rowspan="1">y-coordinate</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>2</td>		<td align="center" colspan="1" rowspan="1">2</td>
	<td>d</td>		<td align="center" colspan="1" rowspan="1">d</td>
	<td>-4</td>		<td align="center" colspan="1" rowspan="1">-4</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>Private key</td>		<td align="left" colspan="1" rowspan="1">Private key</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	</section>		</section>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-7.2
			">
	<name>Octet Key Pair</name>		<name slugifiedName="name-octet-key-pair">Octet Key Pair</name>
	<t>A new key type is defined for Octet Key Pairs (OKP). Do not assume t		<t indent="0" pn="section-7.2-1">A new key type is defined for Octet Key
	hat keys using this type are elliptic curves. This key type could be used for o		Pairs (OKPs). Do not assume that keys using this type are elliptic curves. Th
	ther curve types (for example, mathematics based on hyper-elliptic surfaces). <		is key type could be used for other curve types (for example, mathematics based
	/t>		on hyper-elliptic surfaces). </t>
	<t>The key parameters defined in this section are summarized in <xref ta		<t indent="0" pn="section-7.2-2">The key parameters defined in this sect
	rget="x-table-ec1-keys"/>. The members that are defined for this key type are:		ion are summarized in <xref target="x-table-ec1-keys" format="default" sectionFo
			rmat="of" derivedContent="Table 20"/>. The members that are defined for this ke
			y type are:
	</t>		</t>
			<dl newline="false" indent="6" spacing="normal" pn="section-7.2-3">
	<dl newline="false" indent="5">		<dt pn="section-7.2-3.1">crv:</dt>
	<dt>crv:</dt>		<dd pn="section-7.2-3.2">This contains an identifier of the curve to b
			e used with the key. The curves defined in this document for this key type can b
	<dd>This contains an identifier of the curve to be used with the key.		e found in <xref target="x-table-ec-curves" format="default" sectionFormat="of"
	The curves defined in this document for this key type can be found in <xref targ		derivedContent="Table 18"/>. Other curves may be registered in the future, and
	et="x-table-ec-curves"/>. Other curves may be registered in the future and priv		private curves can be used as well. </dd>
	ate curves can be used as well. </dd>		<dt pn="section-7.2-3.3">x:</dt>
	<dt>x:</dt>		<dd pn="section-7.2-3.4">This contains the public key. The byte strin
			g contains the public key as defined by the algorithm. (For X25519, internally i
	<dd>This contains the public key. The byte string contains the public		t is a little-endian integer.) </dd>
	key as defined by the algorithm. (For X25519, internally it is a little-endian		<dt pn="section-7.2-3.5">d:</dt>
	integer.) </dd>		<dd pn="section-7.2-3.6">This contains the private key. </dd>
	<dt>d:</dt>
	<dd>This contains the private key. </dd>
	</dl>		</dl>
	<t>For public keys, it is <bcp14>REQUIRED</bcp14> that 'crv' and 'x' be		<t indent="0" pn="section-7.2-4">For public keys, it is <bcp14>REQUIRED<
	present in the structure. For private keys, it is <bcp14>REQUIRED</bcp14> that		/bcp14> that "crv" and "x" be present in the structure. For private keys, it i
	'crv' and 'd' be present in the structure. For private keys, it is <bcp14>RECO		s <bcp14>REQUIRED</bcp14> that "crv" and "d" be present in the structure. For p
	MMENDED</bcp14> that 'x' also be present, but it can be recomputed from the requ		rivate keys, it is <bcp14>RECOMMENDED</bcp14> that "x" also be present, but it c
	ired elements and omitting it saves on space. </t>		an be recomputed from the required elements, and omitting it saves on space. </
	<table anchor="x-table-ec1-keys" align="center">		t>
			<table anchor="x-table-ec1-keys" align="center" pn="table-20">
	<name>Octet Key Pair Parameters</name>		<name slugifiedName="name-octet-key-pair-parameters">Octet Key Pair Pa
			rameters</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Key Type</th>		<th align="center" colspan="1" rowspan="1">Key Type</th>
	<th>Label</th>		<th align="center" colspan="1" rowspan="1">Label</th>
	<th>Type</th>		<th align="left" colspan="1" rowspan="1">Type</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>crv</td>		<td align="left" colspan="1" rowspan="1">crv</td>
	<td>1</td>		<td align="center" colspan="1" rowspan="1">1</td>
	<td>-1</td>		<td align="center" colspan="1" rowspan="1">-1</td>
	<td>int / tstr</td>		<td align="left" colspan="1" rowspan="1">int / tstr</td>
	<td>EC identifier - Taken from the "COSE Elliptic Curves" registry		<td align="left" colspan="1" rowspan="1">EC identifier -- Taken fr
	</td>		om the "COSE Elliptic Curves" registry</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>x</td>		<td align="left" colspan="1" rowspan="1">x</td>
	<td>1</td>		<td align="center" colspan="1" rowspan="1">1</td>
	<td>-2</td>		<td align="center" colspan="1" rowspan="1">-2</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>Public Key</td>		<td align="left" colspan="1" rowspan="1">Public Key</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>d</td>		<td align="left" colspan="1" rowspan="1">d</td>
	<td>1</td>		<td align="center" colspan="1" rowspan="1">1</td>
	<td>-4</td>		<td align="center" colspan="1" rowspan="1">-4</td>
	<td>bstr</td>		<td align="left" colspan="1" rowspan="1">bstr</td>
	<td>Private key</td>		<td align="left" colspan="1" rowspan="1">Private key</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	</section>		</section>
	<section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-7.3
			">
	<name>Symmetric Keys</name>		<name slugifiedName="name-symmetric-keys">Symmetric Keys</name>
	<t>Occasionally it is required that a symmetric key be transported betwe		<t indent="0" pn="section-7.3-1">Occasionally, it is required that a sym
	en entities. This key structure allows for that to happen. </t>		metric key be transported between entities. This key structure allows for that
	<t>For symmetric keys, the 'kty' member is set to 4 ('Symmetric'). The		to happen. </t>
	member that is defined for this key type is:		<t indent="0" pn="section-7.3-2">For symmetric keys, the "kty" member is
			set to 4 ("Symmetric"). The member that is defined for this key type is:
	</t>		</t>
			<dl newline="false" indent="3" spacing="normal" pn="section-7.3-3">
	<dl newline="false">		<dt pn="section-7.3-3.1">k:</dt>
	<dt>k:</dt>		<dd pn="section-7.3-3.2">This contains the value of the key. </dd>
	<dd>This contains the value of the key. </dd>
	</dl>		</dl>
	<t>This key structure does not have a form that contains only public mem		<t indent="0" pn="section-7.3-4">This key structure does not have a form
	bers. As it is expected that this key structure is going to be transmitted, car		that contains only public members. As it is expected that this key structure i
	e must be taken that it is never transmitted accidentally or insecurely. For sy		s going to be transmitted, care must be taken that it is never transmitted accid
	mmetric keys, it is <bcp14>REQUIRED</bcp14> that 'k' be present in the structure		entally or insecurely. For symmetric keys, it is <bcp14>REQUIRED</bcp14> that "
	. </t>		k" be present in the structure. </t>
	<table anchor="x-table-symmetric-keys" align="center">		<table anchor="x-table-symmetric-keys" align="center" pn="table-21">
			<name slugifiedName="name-symmetric-key-parameters">Symmetric Key Para
	<name>Symmetric Key Parameters</name>		meters</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="center" colspan="1" rowspan="1">Name</th>
	<th>Key Type</th>		<th align="center" colspan="1" rowspan="1">Key Type</th>
	<th>Label</th>		<th align="center" colspan="1" rowspan="1">Label</th>
	<th>Type</th>		<th align="center" colspan="1" rowspan="1">Type</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>k</td>		<td align="center" colspan="1" rowspan="1">k</td>
	<td>4</td>		<td align="center" colspan="1" rowspan="1">4</td>
	<td>-1</td>		<td align="center" colspan="1" rowspan="1">-1</td>
	<td>bstr</td>		<td align="center" colspan="1" rowspan="1">bstr</td>
	<td>Key Value</td>		<td align="left" colspan="1" rowspan="1">Key Value</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	</section>		</section>
	</section>		</section>
			<section anchor="COSE-Capabilities" numbered="true" removeInRFC="false" toc=
			"include" pn="section-8">
			<name slugifiedName="name-cose-capabilities">COSE Capabilities</name>
			<t indent="0" pn="section-8-1">
	<section anchor="COSE-Capabilities">		The capabilities of an algorithm or key type need to be
	<name>COSE Capabilities</name>		specified in some situations.
	<t>		This has a counterpart
	There are some situations that have been identified where identification		in the S/MIME specifications, where SMIMECapabilities is
	of capabilities of an algorithm or a key type need to be specified.		defined in <xref target="RFC8551" section="2.5.2" sectionFormat="of" for
	One example of this is in <xref target="I-D.ietf-core-oscore-groupcomm"/		mat="default" derivedLink="https://rfc-editor.org/rfc/rfc8551#section-2.5.2" der
	> where the capabilities of the counter signature algorithm are mixed into the t		ivedContent="RFC8551"/>. This document defines the same concept
	raffic key derivation process.		for COSE.
	This has a counterpart in the S/MIME specifications where SMIMECapabilit
	ies is defined in <xref target="RFC8551" section="2.5a.2"/>.
	This document defines the same concept for COSE.
	</t>		</t>
			<t indent="0" pn="section-8-2">
	<t>		The algorithm identifier is not included in the capabilities data, as
	The algorithm identifier is not included in the capabilities data as it		it should be encoded elsewhere in the message. The key type identifier
	should be encoded elsewhere in the message.		is included in the capabilities data, as it is not expected to be
	The key type identifier is included in the capabilities data as it is no		encoded elsewhere.
	t expected to be encoded elsewhere.
	</t>		</t>
			<t indent="0" pn="section-8-3">
	<t>
	Two different types of capabilities are defined: capabilities for algori thms and capabilities for key type.		Two different types of capabilities are defined: capabilities for algori thms and capabilities for key type.
	Once defined by registration with IANA, the list of capabilities for an algorithm or key type is immutable.		Once defined by registration with IANA, the list of capabilities for an algorithm or key type is immutable.
	If it is later found that a new capability is needed for a key type or a n algorithm, it will require that a new code point be assigned to deal with that .		If it is later found that a new capability is needed for a key type or a lgorithm, it will require that a new code point be assigned to deal with that.
	As a general rule, the capabilities are going to map to algorithm-specif ic header parameters or key parameters, but they do not need to do so.		As a general rule, the capabilities are going to map to algorithm-specif ic header parameters or key parameters, but they do not need to do so.
	An example of this is the HSS-LMS key capabilities defined below where t he hash algorithm used is included.		An example of this is the HSS-LMS key type capabilities defined below, w here the hash algorithm used is included.
	</t>		</t>
			<t indent="0" pn="section-8-4">
	<t>		The capability structure is an array of values; the values included in t
	The capability structure is an array of values, the values included in t		he structure are dependent on a specific algorithm or key type.
	he structure are dependent on a specific algorithm or key type.		For algorithm capabilities, the first element should always be a
	For algorithm capabilities, the first element should always be a key typ		key type value if applicable, but the items that are specific to a key
	e value if applicable, but the items that are specific to a key (for example a c		(for example, a curve) should not be included in the algorithm
	urve) should not be included in the algorithm capabilities.		capabilities.
	This means that if one wishes to enumerate all of the capabilities for a		This means that if one wishes to enumerate all of the capabilities for
	device which implements ECDH, it requires that all of the combinations of algor		a device that implements ECDH, it requires that all of the
	ithms and key pairs to be specified.		combinations of algorithms and key pairs be specified.
	The last example of <xref target="cap-examples"/> provides a case where		The last example of <xref target="cap-examples" format="default" section
	this is done by allowing for a cross product to be specified between an array of		Format="of" derivedContent="Section 8.3"/> provides a case
	algorithm capabilities and key type capabilities (see ECDH-ES+A25KW element).		where this is done by allowing for a cross product to be specified
			between an array of algorithm capabilities and key type capabilities
			(see the ECDH-ES+A25KW element).
	For a key, the first element should be the key type value.		For a key, the first element should be the key type value.
	While this means that the key type value will be duplicated if both an a lgorithm and key capability are used, the key type is needed in order to underst and the rest of the values.		While this means that the key type value will be duplicated if both an a lgorithm and key capability are used, the key type is needed in order to underst and the rest of the values.
	</t>		</t>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-8.1
	<section>		">
	<name>Assignments for Existing Algorithms</name>		<name slugifiedName="name-assignments-for-existing-al">Assignments for E
	<t>		xisting Algorithms</name>
	For the current set of algorithms in the registry, those in this docum		<t indent="0" pn="section-8.1-1">
	ent as well as those in <xref target="RFC8230"/> and <xref target="I-D.ietf-cose		For the current set of algorithms in the registry other than IV-GENERA
	-hash-sig"/>, the capabilities list is an array with one element, the key type (		TION (those in this document as well as those in <xref target="RFC8230" format="
	from the "COSE Key Types" Registry).		default" sectionFormat="of" derivedContent="RFC8230"/>, <xref target="RFC8778" f
	It is expected that future registered algorithms could have zero, one,		ormat="default" sectionFormat="of" derivedContent="RFC8778"/>, and <xref target=
	or multiple elements.		"RFC9021" format="default" sectionFormat="of" derivedContent="RFC9021"/>), the c
			apabilities list is an array with one element, the key type (from the "COSE Key
			Types" Registry). It is expected that future registered algorithms could have z
			ero, one, or multiple elements.
	</t>		</t>
	</section>		</section>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-8.2
	<section>		">
	<name>Assignments for Existing Key Types</name>		<name slugifiedName="name-assignments-for-existing-ke">Assignments for E
	<t>		xisting Key Types</name>
	There are a number of pre-existing key types, the following deals with		<t indent="0" pn="section-8.2-1">
	creating the capability definition for those structures:		There are a number of pre-existing key types; the following deals with
	</t>		creating the capability definition for those structures:
	<ul>		</t>
	<li>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-8
	<t>OKP, EC2: The list of capabilities is:</t>		.2-2">
	<ul>		<li pn="section-8.2-2.1">
	<li>The key type value. (1 for OKP or 2 for EC2.)</li>		<t indent="0" pn="section-8.2-2.1.1">OKP, EC2: The list of capabilit
	<li>One curve for that key type from the "COSE Elliptic Curve" reg		ies is:</t>
	istry.</li>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="secti
			on-8.2-2.1.2">
			<li pn="section-8.2-2.1.2.1">The key type value. (1 for OKP or 2
			for EC2.)</li>
			<li pn="section-8.2-2.1.2.2">One curve for that key type from the
			"COSE Elliptic Curves" registry.</li>
	</ul>		</ul>
	</li>		</li>
	<li>		<li pn="section-8.2-2.2">
	<t>RSA: The list of capabilities is:</t>		<t indent="0" pn="section-8.2-2.2.1">RSA: The list of capabilities i
	<ul>		s:</t>
	<li>The key type value (3).</li>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="secti
			on-8.2-2.2.2">
			<li pn="section-8.2-2.2.2.1">The key type value (3).</li>
	</ul>		</ul>
	</li>		</li>
	<li>		<li pn="section-8.2-2.3">
	<t>Symmetric: The list of capabilities is:</t>		<t indent="0" pn="section-8.2-2.3.1">Symmetric: The list of capabili
	<ul>		ties is:</t>
	<li>The key type value (4).</li>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="secti
			on-8.2-2.3.2">
			<li pn="section-8.2-2.3.2.1">The key type value (4).</li>
	</ul>		</ul>
	</li>		</li>
	<li>		<li pn="section-8.2-2.4">
	<t>HSS-LMS: The list of capabilities is:</t>		<t indent="0" pn="section-8.2-2.4.1">HSS-LMS: The list of capabiliti
	<ul>		es is:</t>
	<li>The key type value (5),</li>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="secti
	<li>Algorithm identifier for the underlying hash function from the		on-8.2-2.4.2">
	"COSE Algorithms" registry.</li>		<li pn="section-8.2-2.4.2.1">The key type value (5).</li>
			<li pn="section-8.2-2.4.2.2">Algorithm identifier for the underlyi
			ng hash function from the "COSE
			Algorithms" registry.</li>
			</ul>
			</li>
			<li pn="section-8.2-2.5">
			<t indent="0" pn="section-8.2-2.5.1">WalnutDSA: The list of capabili
			ties is:</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="secti
			on-8.2-2.5.2">
			<li pn="section-8.2-2.5.2.1">The key type value (6).</li>
			<li pn="section-8.2-2.5.2.2">The N value (group and matrix size) f
			or the key, a uint.</li>
			<li pn="section-8.2-2.5.2.3">The q value (finite field order) for
			the key, a uint.</li>
	</ul>		</ul>
	</li>		</li>
	</ul>		</ul>
	</section>		</section>
			<section anchor="cap-examples" numbered="true" removeInRFC="false" toc="in
	<section anchor="cap-examples">		clude" pn="section-8.3">
	<name>Examples</name>		<name slugifiedName="name-examples-2">Examples</name>
	<t>		<t indent="0" pn="section-8.3-1">
	Capabilities can be use in a key derivation process to make sure that		Capabilities can be used in a key derivation process to make sure
	both sides are using the same parameters.		that both sides are using the same parameters.
	This is the approach that is being used by the group communication KDF		The three examples below show different ways that one might utilize pa
	in <xref target="I-D.ietf-core-oscore-groupcomm"/>.		rameters in specifying an application protocol:
	The three examples below show different ways that one might include th
	ings:
	</t>		</t>
	<ul>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-8
	<li>		.3-2">
	Just an algorithm capability: This is useful if the protocol wants to		<li pn="section-8.3-2.1">
	require a specific algorithm such as ECDSA, but it is agnostic about which curve		Only an algorithm capability: This is useful if the protocol wants to
	is being used.		require a specific algorithm, such as ES256, but it is agnostic about which curv
	This does require that the algorithm identifier be specified in the pr		e is being used.
	otocol. See the first example.		This requires that the algorithm identifier be specified in the protoc
			ol. See the first example.
	</li>		</li>
	<li>		<li pn="section-8.3-2.2">
	Just a key type capability: This is useful if the protccol wants to		Only a key type capability: This is useful if the protocol wants
	require a specific a specific key type and curve, such as P-256, but will accept		to require a specific key type and curve, such as
	any algorithm using that curve (e.g. both ECDSA and ECDH).		P-256, but will accept any algorithm using that curve (e.g., both
			ECDSA and ECDH).
	See the second example.		See the second example.
	</li>		</li>
	<li>		<li pn="section-8.3-2.3">
	Both an algorithm and a key type capability: This is used if the pr		Both algorithm and key type capabilities: This is used if the
	otocol needs to nail down all of the options surrounding an algorithm E.g. EdDS		protocol needs to nail down all of the options surrounding an
	A with the curve X25519.		algorithm -- e.g., EdDSA with the curve Ed25519.
	As with the first example, the algorithm identifier needs to be spec		As with the first example, the algorithm identifier needs to be spec
	ified in the protocol. See the third example which just concatenates the two cap		ified in the protocol. See the third example, which just concatenates the two ca
	abilities together.		pabilities together.
	</li>		</li>
	</ul>		</ul>
			<sourcecode type="cbor-pretty" markers="false" pn="section-8.3-3">
	<artwork>		Algorithm ES256
	Algorithm ECDSA
	0x8102 / [2 \ EC2 \ ] /		0x8102 / [2 \ EC2 \ ] /
	Key type EC2 with P-256 curve:		Key type EC2 with P-256 curve:
	0x820201 / [2 \ EC2 \, 1 \ P-256 \] /		0x820201 / [2 \ EC2 \, 1 \ P-256 \] /
	ECDH-ES + A256KW with an X25519 curve:		ECDH-ES + A256KW with an X25519 curve:
	0x8101820104 / [1 \ OKP \],[1 \ OKP \, 4 \ X25519 \] /		0x8101820104 / [1 \ OKP \],[1 \ OKP \, 4 \ X25519 \] /
	</artwork>		</sourcecode>
			<t indent="0" pn="section-8.3-4">
	<t>		The capabilities can also be used by an entity to advertise what it is
	The capabilities can also be used by and entity to advertise what it i		capable of doing.
	s capabable of doing.		The decoded example below is one of many encodings that could be used
	The decoded example below is one of many encoding that could be used f		for that purpose.
	or that purpose.
	Each array element includes three fields: the algorithm identifier, on e or more algorithm capabilities, and one or more key type capabilities.		Each array element includes three fields: the algorithm identifier, on e or more algorithm capabilities, and one or more key type capabilities.
	</t>		</t>
			<sourcecode type="cbor-diag" markers="false" pn="section-8.3-5">
	<artwork>
	[		[
	[-8 / EdDSA /,		[-8 / EdDSA /,
	[1 / OKP key type /],		[1 / OKP key type /],
	[		[
	[1 / OKP /, 6 / Ed25519 / ],		[1 / OKP /, 6 / Ed25519 / ],
	[1 /OKP/, 7 /Ed448 /]		[1 /OKP/, 7 /Ed448 /]
	]		]
	],		],
	[-7 / ECDSA with SHA-256/,		[-7 / ECDSA with SHA-256/,
	[2 /EC2 key type/],		[2 /EC2 key type/],
	skipping to change at line 1844 ¶		skipping to change at line 2314 ¶
	[		[
	[2 /EC2/, 1 /P-256/],		[2 /EC2/, 1 /P-256/],
	[1 /OKP/, 4 / X25519/ ]		[1 /OKP/, 4 / X25519/ ]
	]		]
	],		],
	[ 1 / A128GCM /,		[ 1 / A128GCM /,
	[ 4 / Symmetric / ],		[ 4 / Symmetric / ],
	[ 4 / Symmetric /]		[ 4 / Symmetric /]
	]		]
	]		]
	</artwork>		</sourcecode>
	<t>		<t indent="0" pn="section-8.3-6">
	Examining the above:		Examining the above:
	</t>		</t>
	<ul>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-8
	<li>The first element indicates that the entity supports EdDSA with cu		.3-7">
	rves Ed25519 and Ed448.</li>		<li pn="section-8.3-7.1">The first element indicates that the entity s
	<li>The second element indicates that the entity supports ECDSA with c		upports EdDSA with curves Ed25519 and Ed448.</li>
	urves P-256 and P-521.</li>		<li pn="section-8.3-7.2">The second element indicates that the entity
	<li>		supports ECDSA with SHA-256 with curves P-256 and P-521.</li>
	The third element indicates that the entity support ephemeral-static		<li pn="section-8.3-7.3">
	ECDH using AES256 key wrap.		The third element indicates that the entity supports Ephemeral-Stati
			c ECDH using AES256 key wrap.
	The entity can support the P-256 curve with an EC2 key type and the X25519 curve with an OKP key type.		The entity can support the P-256 curve with an EC2 key type and the X25519 curve with an OKP key type.
	</li>		</li>
	<li>The last element indicates that the entity supports AES-GCM of 128 bits for content encryption.</li>		<li pn="section-8.3-7.4">The last element indicates that the entity su pports AES-GCM of 128 bits for content encryption.</li>
	</ul>		</ul>
	<t>		<t indent="0" pn="section-8.3-8">
	The entity does not advertise that it supports any MAC algorithms.		The entity does not advertise that it supports any MAC algorithms.
	</t>		</t>
	</section>		</section>
	</section>		</section>
			<section anchor="CBOR-Canonical" numbered="true" removeInRFC="false" toc="in
	<section anchor="CBOR-Canonical">		clude" pn="section-9">
			<name slugifiedName="name-cbor-encoding-restrictions">CBOR Encoding Restri
	<name>CBOR Encoding Restrictions</name>		ctions</name>
	<t>This document limits the restrictions it imposes on how the CBOR Encode		<t indent="0" pn="section-9-1">This document limits the restrictions it im
	r needs to work.		poses on how the CBOR
	It has been narrowed down to the following restrictions: </t>		Encoder needs to work. The new encoding restrictions are aligned with
			the Core Deterministic Encoding Requirements specified in <xref sectionFormat=
	<ul>		"of" section="4.2.1" target="STD94" format="default" derivedLink="https://rfc-ed
			itor.org/rfc/rfc8949#section-4.2.1" derivedContent="STD94">RFC 8949</xref>.
	<li>		It has been narrowed down to the following restrictions:</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-9-2
			">
			<li pn="section-9-2.1">
	The restriction applies to the encoding of the COSE_KDF_Context.		The restriction applies to the encoding of the COSE_KDF_Context.
	</li>		</li>
			<li pn="section-9-2.2">
	<li>		Encoding <bcp14>MUST</bcp14> be done using definite lengths,
	Encoding <bcp14>MUST</bcp14> be done using definite lengths and the le		and the length of the (encoded) argument <bcp14>MUST</bcp14>
	ngth of the <bcp14>MUST</bcp14> be the minimum possible length.		be the minimum possible length. This means that the integer
	This means that the integer 1 is encoded as "0x01" and not "0x1801".		1 is encoded as "0x01" and not "0x1801".
	</li>		</li>
			<li pn="section-9-2.3">
	<li>
	Applications <bcp14>MUST NOT</bcp14> generate messages with the same l abel used twice as a key in a single map.		Applications <bcp14>MUST NOT</bcp14> generate messages with the same l abel used twice as a key in a single map.
	Applications <bcp14>MUST NOT</bcp14> parse and process messages with t		Applications <bcp14>MUST NOT</bcp14> parse and process messages with
	he same label used twice as a key in a single map.		the same label used twice as a key in a single map.
	Applications can enforce the parse and process requirement by using pa		Applications can enforce the parse-and-process
	rsers that will fail the parse step or by using parsers that will pass all keys		requirement by using parsers that will fail the parse step or by
	to the application, and the application can perform the check for duplicate keys		using parsers that will pass all keys to the application, and the
	.		application can perform the check for duplicate keys.
	</li>		</li>
	</ul>		</ul>
	</section>		</section>
			<section anchor="iana-considerations" numbered="true" removeInRFC="false" to
	<section anchor="iana-considerations">		c="include" pn="section-10">
			<name slugifiedName="name-iana-considerations">IANA Considerations</name>
	<name>IANA Considerations</name>		<t indent="0" pn="section-10-1">IANA has updated all COSE registries excep
	<section>		t for "COSE
	<name>Changes to "COSE Key Types" registry.</name>		Header Parameters" and "COSE Key Common Parameters" to point to this docum
	<t>		ent instead of <xref target="RFC8152" format="default" sectionFormat="of" derive
	IANA is requested to create a new column in the "COSE Key Types" registr		dContent="RFC8152"/>.</t>
	y.		<section numbered="true" removeInRFC="false" toc="include" pn="section-10.
	The new column is to be labeled "Capabilities".		1">
	The new column is to be populated according the entries in <xref target=		<name slugifiedName="name-changes-to-the-cose-key-typ">Changes to the "C
	"initial-kty-caps"/>.		OSE Key Types" Registry</name>
	</t>		<t indent="0" pn="section-10.1-1">
			IANA has added a new column in the "COSE Key Types" registry.
	<table anchor="initial-kty-caps">		The new column is labeled "Capabilities" and has been populated accordin
	<name>Key Type Capabilities</name>		g to the entries in <xref target="initial-kty-caps" format="default" sectionForm
			at="of" derivedContent="Table 22"/>.
			</t>
			<table anchor="initial-kty-caps" align="center" pn="table-22">
			<name slugifiedName="name-key-type-capabilities">Key Type Capabilities
			</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Value</th>		<th align="left" colspan="1" rowspan="1">Value</th>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Capabilities</th>		<th align="left" colspan="1" rowspan="1">Capabilities</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>1</td>		<td align="left" colspan="1" rowspan="1">1</td>
	<td>OKP</td>		<td align="left" colspan="1" rowspan="1">OKP</td>
	<td>[kty(1), crv]</td>		<td align="left" colspan="1" rowspan="1">[kty(1), crv]</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>2</td>		<td align="left" colspan="1" rowspan="1">2</td>
	<td>EC2</td>		<td align="left" colspan="1" rowspan="1">EC2</td>
	<td>[kty(2), crv]</td>		<td align="left" colspan="1" rowspan="1">[kty(2), crv]</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>3</td>		<td align="left" colspan="1" rowspan="1">3</td>
	<td>RSA</td>		<td align="left" colspan="1" rowspan="1">RSA</td>
	<td>[kty(3)]</td>		<td align="left" colspan="1" rowspan="1">[kty(3)]</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>4</td>		<td align="left" colspan="1" rowspan="1">4</td>
	<td>Symmetric</td>		<td align="left" colspan="1" rowspan="1">Symmetric</td>
	<td>[kty(4)]</td>		<td align="left" colspan="1" rowspan="1">[kty(4)]</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>5</td>		<td align="left" colspan="1" rowspan="1">5</td>
	<td>HSS-LMS</td>		<td align="left" colspan="1" rowspan="1">HSS-LMS</td>
	<td>[kty(5), hash algorithm]</td>		<td align="left" colspan="1" rowspan="1">[kty(5), hash algorithm]<
			/td>
			</tr>
			<tr>
			<td align="left" colspan="1" rowspan="1">6</td>
			<td align="left" colspan="1" rowspan="1">WalnutDSA</td>
			<td align="left" colspan="1" rowspan="1">[kty(6), N value, q value
			]</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	<t>
	IANA is requested to update the pointer for expert review to [[this do
	cument]].
	</t>
	</section>		</section>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-10.
	<section>		2">
	<name>Changes to "COSE Algorithms" registry</name>		<name slugifiedName="name-changes-to-the-cose-algorit">Changes to the "C
	<t>		OSE Algorithms" Registry</name>
	IANA is requested to create a new column in the "COSE Algorithms" regi		<t indent="0" pn="section-10.2-1">
	stry.		IANA has added a new column in the "COSE Algorithms" registry.
	The new column is to be labeled "Capabilities".		The new column is labeled "Capabilities" and has been populated with "
	The new column is populated with "[kty]" for all current, non-provisio		[kty]" for all current,
	nal, registrations.		nonprovisional registrations.
	It is expected that the documents which define those algorithms will b
	e expanded to include this registration.
	If this is not done then the Designated Expert should be consulted bef
	ore final registration for this document is done.
	</t>
	<t>
	IANA is requested to update all references from RFC 8152 to [[This Doc
	ument]].
	</t>
	<t>
	IANA is requested to update the pointer for expert rview to [[this doc
	ument]].
	</t>		</t>
	<t>		<t indent="0" pn="section-10.2-2">
	IANA is requested to update the reference column in the "COSE Algorith		IANA has updated the Reference column in the "COSE Algorithms" registr
	ms" registry to include [[This Document]] as a reference for all rows where it i		y to include this document as a reference for all rows where it was not already
	s not already present.		present.
	</t>		</t>
			<t indent="0" pn="section-10.2-3">
	<t>		IANA has added a new row to the "COSE Algorithms" registry.
	IANA is requested to add a new row to the "COSE Algorithms" registry.
	</t>		</t>
			<table align="center" pn="table-23">
	<table>		<name slugifiedName="name-new-entry-in-the-cose-algor">New entry in th
			e COSE Algorithms registry</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="left" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	<th>Reference</th>		<th align="left" colspan="1" rowspan="1">Reference</th>
	<th>Recommended</th>		<th align="left" colspan="1" rowspan="1">Recommended</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>IV Generation</td>		<td align="left" colspan="1" rowspan="1">IV-GENERATION</td>
	<td>IV-GENERATION</td>		<td align="left" colspan="1" rowspan="1">34</td>
	<td>For doing IV generation for symmetric algorithms.</td>		<td align="left" colspan="1" rowspan="1">For doing IV generation f
	<td>[[THIS DOCUMENT]]</td>		or symmetric algorithms.</td>
	<td>No</td>		<td align="left" colspan="1" rowspan="1">RFC 9053</td>
			<td align="left" colspan="1" rowspan="1">No</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
			<t indent="0" pn="section-10.2-5">
	<t>		The Capabilities column for this registration is to be empty.
	The capabilities column for this registration is to be empty.
	</t>		</t>
	</section>		</section>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-10.
	<section>		3">
	<name>Changes to the "COSE Key Type Parameters" registry</name>		<name slugifiedName="name-changes-to-the-cose-key-type">Changes to the "
	<t>		COSE Key Type Parameters" Registry</name>
	IANA is requested to modify the description to "Public Key" for the li		<t indent="0" pn="section-10.3-1">
	ne with "Key Type" of 2 and the "Name" of "x".		IANA has modified the description to "Public Key" for the
	See <xref target="x-table-ec1-keys"/> which has been modified with thi		line with "Key Type" of 1 and the "Name" of "x".
	s change.		See <xref target="x-table-ec1-keys" format="default" sectionFormat="of
	</t>		" derivedContent="Table 20"/>, which has been modified with
	<t>		this change.
	IANA is requested to update the references in the table from RFC8152 t
	o [[This Document]].
	</t>
	<t>
	IANA is requested to update the pointer for expert rview to [[this doc
	ument]].
	</t>		</t>
	</section>		</section>
			<section anchor="review" numbered="true" removeInRFC="false" toc="include"
	<section anchor="IANA-Alg-Registry">		pn="section-10.4">
	<name>COSE Header Algorithm Parameters Registry</name>		<name slugifiedName="name-expert-review-instructions">Expert Review Inst
	<t>		ructions</name>
	IANA created a registry titled "COSE Header Algorithm Parameters" as		<t indent="0" pn="section-10.4-1">
	part of processing <xref target="RFC8152"/>.		All of the IANA registries established by <xref target="RFC8152" forma
	The registry has been created to use the "Expert Review Required" regi		t="default" sectionFormat="of" derivedContent="RFC8152"/> are, at least in part,
	stration procedure <xref target="RFC8126"/>.		defined as Expert Review <xref target="RFC8126" format="default" sectionFormat=
	</t>		"of" derivedContent="RFC8126"/>. This section gives some general guidelines for
	<t>		what the experts should be looking for, but they are being designated as expert
	IANA is requested to update the references from <xref target="RFC8152"		s for a reason, so they should be given substantial latitude.
	/> to this document.
	</t>		</t>
	<t>		<t indent="0" pn="section-10.4-2">Expert reviewers should take the follo
	IANA is requested to update the pointer for expert rview to [[this doc		wing into consideration:
	ument]].
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-1
			0.4-3">
			<li pn="section-10.4-3.1">Point squatting should be discouraged. Revi
			ewers are encouraged to get sufficient information for registration requests to
			ensure that the usage is not going to duplicate an existing registration and tha
			t the code point is likely to be used in deployments. The ranges tagged as priv
			ate use are intended for testing purposes and closed environments; code points i
			n other ranges should not be assigned for testing. </li>
			<li pn="section-10.4-3.2">Standards Track or BCP RFCs are required to
			register a code point in the Standards Action range.
			Specifications should exist for Specification Required ranges,
			but early assignment before an RFC is available is considered to be
			permissible. Specifications are needed for the first-come, first-served range
			if the points are expected to be used outside of closed environments in an
			interoperable way. When specifications are not provided, the description
			provided needs to have sufficient information to identify what the point is
			being used for. </li>
			<li pn="section-10.4-3.3">Experts should take into account the expecte
			d usage of fields when
			approving code point assignment.
			The fact that the Standards Action range is only available to Standards Track do
			cuments does not mean that a Standards Track document cannot have points assigne
			d outside of that range. The length of the encoded value should
			be weighed against how many code points of that length are left and the size of
			device it will be used on.</li>
			<li pn="section-10.4-3.4">When algorithms are registered, vanity regis
			trations should be discouraged. One way to do this is to require registrations
			to provide additional documentation on security analysis of the algorithm. Anot
			her thing that should be considered is requesting an opinion on the algorithm fr
			om the Crypto Forum Research Group (CFRG). Algorithms are expected to meet the s
			ecurity requirements of the
			community and the requirements of the message structures in order to be
			suitable for registration.
			</li>
			</ul>
	</section>		</section>
	<section title="Expert Review Instructions" anchor="review" >
	<t>
	All of the IANA registries established by <xref target="RFC8152"/> are
	, at least in part, defined as expert review. This section gives some general g
	uidelines for what the experts should be looking for, but they are being designa
	ted as experts for a reason, so they should be given substantial latitude.
	</t>
	<t>Expert reviewers should take into consideration the following points:
	</t>
	<ul>
	<li>Point squatting should be discouraged. Reviewers are encouraged to get suff
	icient information for registration requests to ensure that the usage is not goi
	ng to duplicate one that is already registered, and that the point is likely to
	be used in deployments. The zones tagged as private use are intended for testin
	g purposes and closed environments; code points in other ranges should not be as
	signed for testing. </li>
	<li>Specifications are required for the standards track range of point assignmen
	t. Specifications should exist for specification required ranges, but early ass
	ignment before a specification is available is considered to be permissible. Sp
	ecifications are needed for the first-come, first-serve range if they are expect
	ed to be used outside of closed environments in an interoperable way. When spec
	ifications are not provided, the description provided needs to have sufficient i
	nformation to identify what the point is being used for. </li>
	<li>Experts should take into account the expected usage of fields when approving
	point assignment. The fact that there is a range for standards track documents
	does not mean that a standards track document cannot have points assigned outsi
	de of that range. The length of the encoded value should be weighed against how
	many code points of that length are left, the size of device it will be used on
	, and the number of code points left that encode to that size. </li>
	<li>When algorithms are registered, vanity registrations should be discouraged.
	One way to do this is to require registrations to provide additional documentat
	ion on security analysis of the algorithm. Another thing that should be conside
	red is requesting an opinion on the algorithm from the Crypto Forum Research Gro
	up (CFRG). Algorithms that do not meet the security requirements of the communi
	ty and the messages structures should not be registered. </li>
	</ul>
	</section>
	</section>		</section>
			<section anchor="security-considerations" numbered="true" removeInRFC="false
	<section anchor="security-considerations">		" toc="include" pn="section-11">
			<name slugifiedName="name-security-considerations">Security Considerations
	<name>Security Considerations</name>		</name>
	<t>There are a number of security considerations that need to be taken int		<t indent="0" pn="section-11-1">There are a number of security considerati
	o account by implementers of this specification. The security considerations th		ons that need to be taken into account by implementers of this specification. T
	at are specific to an individual algorithm are placed next to the description of		he security considerations that are specific to an individual algorithm are plac
	the algorithm. While some considerations have been highlighted here, additiona		ed next to the description of the algorithm. While some considerations have bee
	l considerations may be found in the documents listed in the references. </t>		n highlighted here, additional considerations may be found in the documents list
	<t>Implementations need to protect the private key material for any indivi		ed in the references. </t>
	duals. There are some cases in this document that need to be highlighted on thi		<t indent="0" pn="section-11-2">Implementations need to protect the privat
	s issue.		e key material for all
			individuals. Some cases in this document need to be highlighted with
			regard to this issue.
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-11-
	<ul>		3">
			<li pn="section-11-3.1">Use of the same key for two different algorithms
	<li>Using the same key for two different algorithms can leak information		can leak information about the key. It is therefore recommended that keys be r
	about the key. It is therefore recommended that keys be restricted to a single		estricted to a single algorithm. </li>
	algorithm. </li>		<li pn="section-11-3.2">Use of "direct" as a recipient algorithm combine
			d with a second recipient algorithm exposes the direct key to the second recipie
	<li>Use of 'direct' as a recipient algorithm combined with a second reci		nt; <xref section="8.5" target="RFC9052" sectionFormat="of" format="default" der
	pient algorithm exposes the direct key to the second recipient. </li>		ivedLink="https://rfc-editor.org/rfc/rfc9052#section-8.5" derivedContent="RFC905
			2"/> forbids combining "direct" recipient algorithms with other modes. </li>
	<li>Several of the algorithms in this document have limits on the number		<li pn="section-11-3.3">Several of the algorithms in this document have
	of times that a key can be used without leaking information about the key. </l		limits on the number of times that a key can be used without leaking information
	i>		about the key. </li>
	</ul>		</ul>
	<t>The use of ECDH and direct plus KDF (with no key wrap) will not directl		<t indent="0" pn="section-11-4">The use of ECDH and direct plus KDF (with
	y lead to the private key being leaked; the one way function of the KDF will pre		no key wrap) will not
	vent that. There is, however, a different issue that needs to be addressed. Ha		directly lead to the private key being leaked; the one-way function of
	ving two recipients requires that the CEK be shared between two recipients. The		the KDF will prevent that. There is, however, a different issue that
	second recipient therefore has a CEK that was derived from material that can be		needs to be addressed. Having two recipients requires that the CEK be
	used for the weak proof of origin. The second recipient could create a message		shared between two recipients. The second recipient therefore has a CEK
	using the same CEK and send it to the first recipient; the first recipient woul		that was derived from material that can be used for the weak proof of
	d, for either static-static ECDH or direct plus KDF, make an assumption that the		origin. The second recipient could create a message using the same CEK
	CEK could be used for proof of origin even though it is from the wrong entity.		and send it to the first recipient; the first recipient would, for
	If the key wrap step is added, then no proof of origin is implied and this is n		either Static-Static ECDH or direct plus KDF, make an assumption that
	ot an issue. </t>		the CEK could be used for proof of origin, even though it is from the
	<t>Although it has been mentioned before, the use of a single key for mult		wrong entity. If the key wrap step is added, then no proof of origin is
	iple algorithms has been demonstrated in some cases to leak information about a		implied and this is not an issue. </t>
	key, provide the opportunity for attackers to forge integrity tags, or gain info		<t indent="0" pn="section-11-5">Although it has been mentioned before, it
	rmation about encrypted content. Binding a key to a single algorithm prevents t		bears repeating that the use of a single key for
	hese problems. Key creators and key consumers are strongly encouraged not only		multiple algorithms has been demonstrated in some cases to leak
	to create new keys for each different algorithm, but to include that selection o		information about a key, providing the opportunity for attackers to forge
	f algorithm in any distribution of key material and strictly enforce the matchin		integrity tags or gain information about encrypted content. Binding a
	g of algorithms in the key structure to algorithms in the message structure. In		key to a single algorithm prevents these problems. Key creators and key
	addition to checking that algorithms are correct, the key form needs to be chec		consumers are strongly encouraged to not only create new keys for each
	ked as well. Do not use an 'EC2' key where an 'OKP' key is expected. </t>		different algorithm, but to include that selection of algorithm in any
	<t>Before using a key for transmission, or before acting on information re		distribution of key material and strictly enforce the matching of
	ceived, a trust decision on a key needs to be made. Is the data or action somet		algorithms in the key structure to algorithms in the message structure.
	hing that the entity associated with the key has a right to see or a right to re		In addition to checking that algorithms are correct, the key form needs
	quest? A number of factors are associated with this trust decision. Some of the		to be checked as well. Do not use an "EC2" key where an "OKP" key is
	ones that are highlighted here are:		expected. </t>
			<t indent="0" pn="section-11-6">Before using a key for transmission, or be
			fore acting on information
			received, a trust decision on a key needs to be made. Is the data or
			action something that the entity associated with the key has a right to
			see or a right to request? A number of factors are associated with this
			trust decision. Some highlighted here are:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-11-
	<ul>		7">
			<li pn="section-11-7.1">What are the permissions associated with the key
	<li>What are the permissions associated with the key owner?</li>		owner?</li>
			<li pn="section-11-7.2">Is the cryptographic algorithm acceptable in the
	<li>Is the cryptographic algorithm acceptable in the current context?</l		current context?</li>
	i>		<li pn="section-11-7.3">Have the restrictions associated with the key, s
			uch as algorithm
	<li>Have the restrictions associated with the key, such as algorithm or		or freshness, been checked, and are they correct?</li>
	freshness, been checked and are they correct?</li>		<li pn="section-11-7.4">Is the request something that is reasonable, giv
			en the current state of the application?</li>
	<li>Is the request something that is reasonable, given the current state		<li pn="section-11-7.5">Have any security considerations that are part o
	of the application?</li>		f the message been enforced (as specified by the application or "crit" header pa
			rameter)?</li>
	<li>Have any security considerations that are part of the message been e
	nforced (as specified by the application or 'crit' parameter)?</li>
	</ul>		</ul>
	<t>There are a large number of algorithms presented in this document that		<t indent="0" pn="section-11-8">There are a large number of algorithms pre
	use nonce values. For all of the nonces defined in this document, there is some		sented in this
	type of restriction on the nonce being a unique value either for a key or for s		document that use nonce values. For all of the nonces defined
	ome other conditions. In all of these cases, there is no known requirement on t		in this document, there is some type of restriction on the nonce
	he nonce being both unique and unpredictable; under these circumstances, it's re		being a unique value for either a key or some other
	asonable to use a counter for creation of the nonce. In cases where one wants t		conditions. In all of these cases, there is no known
	he pattern of the nonce to be unpredictable as well as unique, one can use a key		requirement on the nonce being both unique and unpredictable;
	created for that purpose and encrypt the counter to produce the nonce value. <		under these circumstances, it's reasonable to use a counter for
	/t>		creation of the nonce. In cases where one wants the pattern of
	<t>One area that has been getting exposure is traffic analysis of encrypte		the nonce to be unpredictable as well as unique, one can use a
	d messages based on the length of the message. This specification does not prov		key created for that purpose and encrypt the counter to produce
	ide for a uniform method of providing padding as part of the message structure.		the nonce value. </t>
	An observer can distinguish between two different messages (for example, 'YES'		<t indent="0" pn="section-11-9">One area that has been getting
	and 'NO') based on the length for all of the content encryption algorithms that		exposure is traffic analysis of encrypted messages based on the
	are defined in this document. This means that it is up to the applications to d		length of the message. This specification does not provide
	ocument how content padding is to be done in order to prevent or discourage such		a uniform method for providing padding as part of the message
	analysis. (For example, the text strings could be defined as 'YES' and 'NO '.)		structure. An observer can distinguish between two different
	</t>		messages (for example, "YES" and "NO") based on the length for
	<t>		all of the content encryption algorithms that are defined in
	The analsys done in <xref target="I-D.ietf-quic-tls"/> is based on the n		this document. This means that it is up to the applications to
	umber of records/packets that are sent.		document how content padding is to be done in order to prevent
	This should map well to the number of messages sent when use COSE so tha		or discourage such analysis. (For example, the text strings
	t analysis should hold here as well.		could be defined as "YES" and "NO ".) </t>
	It needs to be noted that the limits are based on the number of messages		<t indent="0" pn="section-11-10"> The analysis done
	, but QUIC and DTLS are always pair-wise based endpoints, <xref target="I-D.ietf		in <xref target="RFC9147" format="default" sectionFormat="of" derivedConte
	-core-oscore-groupcomm"/> use COSE in a group communication.		nt="RFC9147"/> is based on the number of records that
	Under these circumstances it may be that no one single entity will see a		are sent. This should map well to the number of messages sent
	ll of the messages that are encrypted an therefore no single entity can trigger		when using COSE, so that analysis should hold here as well, under
	the rekey operation.		the assumption that the COSE messages are roughly the same size
			as DTLS records.
			It needs to be noted that the limits are based on the number of messages,
			but QUIC and DTLS are always pairwise-based endpoints. In contrast, <xref targ
			et="I-D.ietf-core-oscore-groupcomm" format="default" sectionFormat="of" derivedC
			ontent="OSCORE-GROUPCOMM"/> uses COSE in a group communication scenario. Under
			these circumstances, it may be that no one
			single entity will see all of the messages that are encrypted, and
			therefore no single entity can trigger the rekey operation.
	</t>		</t>
	</section>		</section>
	</middle>		</middle>
	<back>		<back>
	<references>		<displayreference target="I-D.ietf-core-oscore-groupcomm" to="OSCORE-GROUPCO
	<name>References</name>		MM"/>
	<references>		<displayreference target="I-D.mattsson-cfrg-det-sigs-with-noise" to="CFRG-DE
			T-SIGS"/>
	<name>Normative References</name>		<displayreference target="I-D.ietf-cose-countersign" to="COUNTERSIGN"/>
	<xi:include href="reference.I-D.ietf-cose-rfc8152bis-struct.xml"/>		<references pn="section-12">
	<xi:include href="reference.RFC.2104.xml"/>		<name slugifiedName="name-references">References</name>
	<xi:include href="reference.RFC.2119.xml"/>		<references pn="section-12.1">
	<xi:include href="reference.RFC.3394.xml"/>		<name slugifiedName="name-normative-references">Normative References</na
	<xi:include href="reference.RFC.3610.xml"/>		me>
	<xi:include href="reference.RFC.5869.xml"/>		<reference anchor="AES-GCM" target="https://csrc.nist.gov/publications/n
	<xi:include href="reference.RFC.6090.xml"/>		istpubs/800-38D/SP-800-38D.pdf" quoteTitle="true" derivedAnchor="AES-GCM">
	<xi:include href="reference.RFC.6979.xml"/>
	<xi:include href="reference.RFC.7049.xml"/>
	<xi:include href="reference.RFC.8439.xml"/>
	<xi:include href="reference.RFC.7748.xml"/>
	<xi:include href="reference.RFC.8174.xml"/>
	<reference anchor="AES-GCM" target="https://csrc.nist.gov/publications/n
	istpubs/800-38D/SP-800-38D.pdf">
	<front>		<front>
	<title>Recommendation for Block Cipher Modes of Operation: Galois/Co unter Mode (GCM) and GMAC</title>		<title>Recommendation for Block Cipher Modes of Operation: Galois/Co unter Mode (GCM) and GMAC</title>
	<seriesInfo name="DOI" value="10.6028/NIST.SP.800-38D"/>
	<seriesInfo name="NIST Special Publication" value="800-38D"/>		<seriesInfo name="NIST Special Publication" value="800-38D"/>
	<author>		<author initials="M" surname="Dworkin"/>
	<organization>National Institute of Standards and Technology</orga
	nization>
	</author>
	<date year="2007" month="November"/>		<date year="2007" month="November"/>
	</front>		</front>
			<seriesInfo name="DOI" value="10.6028/NIST.SP.800-38D"/>
	</reference>		</reference>
	<reference anchor="DSS" target="http://nvlpubs.nist.gov/nistpubs/FIPS/NI ST.FIPS.186-4.pdf">		<reference anchor="DSS" target="https://nvlpubs.nist.gov/nistpubs/FIPS/N IST.FIPS.186-4.pdf" quoteTitle="true" derivedAnchor="DSS">
	<front>		<front>
	<title>Digital Signature Standard (DSS)</title>		<title>Digital Signature Standard (DSS)</title>
	<seriesInfo name="DOI" value="10.6028/NIST.FIPS.186-4"/>
	<seriesInfo name="FIPS PUB" value="186-4"/>		<seriesInfo name="FIPS PUB" value="186-4"/>
	<author>		<author>
	<organization>National Institute of Standards and Technology</orga nization>		<organization showOnFrontPage="true">National Institute of Standar ds and Technology</organization>
	</author>		</author>
	<date year="2013" month="July"/>		<date year="2013" month="July"/>
	</front>		</front>
			<seriesInfo name="DOI" value="10.6028/NIST.FIPS.186-4"/>
	</reference>		</reference>
	<reference anchor="MAC">		<reference anchor="MAC" target="https://cacr.uwaterloo.ca/hac/" quoteTit
	<!--		le="true" derivedAnchor="MAC">
	RFC Editor - help
	A. Menezes, P. van Oorschot, S. Vanstone,
	Handbook of Applied Cryptography, CRC Press, Inc., Boca Raton
	(1996).
	-->
	<front>		<front>
	<title>Handbook of Applied Cryptography</title>		<title>Handbook of Applied Cryptography</title>
			<author initials="A." surname="Menezes"/>
	<author initials="A." surname="Menees"/>
	<author initials="P." surname="van Oorschot"/>		<author initials="P." surname="van Oorschot"/>
	<author initials="S." surname="Vanstone"/>		<author initials="S." surname="Vanstone"/>
	<date year="1996"/>		<date year="1996"/>
	</front>		</front>
			<refcontent>CRC Press, Boca Raton</refcontent>
	</reference>		</reference>
	<reference anchor="SEC1" target="http://www.secg.org/sec1-v2.pdf">		<reference anchor="RFC2104" target="https://www.rfc-editor.org/info/rfc2
			104" quoteTitle="true" derivedAnchor="RFC2104">
			<front>
			<title>HMAC: Keyed-Hashing for Message Authentication</title>
			<author fullname="H. Krawczyk" initials="H" surname="Krawczyk"/>
			<author fullname="M. Bellare" initials="M" surname="Bellare"/>
			<author fullname="R. Canetti" initials="R" surname="Canetti"/>
			<date month="February" year="1997"/>
			<abstract>
			<t indent="0">This document describes HMAC, a mechanism for messag
			e authentication using cryptographic hash functions. HMAC can be used with any
			iterative cryptographic hash function, e.g., MD5, SHA-1, in combination with a s
			ecret shared key. The cryptographic strength of HMAC depends on the properties
			of the underlying hash function. This memo provides information for the Interne
			t community. This memo does not specify an Internet standard of any kind</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="2104"/>
			<seriesInfo name="DOI" value="10.17487/RFC2104"/>
			</reference>
			<reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2
			119" quoteTitle="true" derivedAnchor="RFC2119">
			<front>
			<title>Key words for use in RFCs to Indicate Requirement Levels</tit
			le>
			<author fullname="S. Bradner" initials="S" surname="Bradner"/>
			<date month="March" year="1997"/>
			<abstract>
			<t indent="0">In many standards track documents several words are
			used to signify the requirements in the specification. These words are often ca
			pitalized. This document defines these words as they should be interpreted in I
			ETF documents. This document specifies an Internet Best Current Practices for t
			he Internet Community, and requests discussion and suggestions for improvements.
			</t>
			</abstract>
			</front>
			<seriesInfo name="BCP" value="14"/>
			<seriesInfo name="RFC" value="2119"/>
			<seriesInfo name="DOI" value="10.17487/RFC2119"/>
			</reference>
			<reference anchor="RFC3394" target="https://www.rfc-editor.org/info/rfc3
			394" quoteTitle="true" derivedAnchor="RFC3394">
			<front>
			<title>Advanced Encryption Standard (AES) Key Wrap Algorithm</title>
			<author fullname="J. Schaad" initials="J" surname="Schaad"/>
			<author fullname="R. Housley" initials="R" surname="Housley"/>
			<date month="September" year="2002"/>
			</front>
			<seriesInfo name="RFC" value="3394"/>
			<seriesInfo name="DOI" value="10.17487/RFC3394"/>
			</reference>
			<reference anchor="RFC3610" target="https://www.rfc-editor.org/info/rfc3
			610" quoteTitle="true" derivedAnchor="RFC3610">
			<front>
			<title>Counter with CBC-MAC (CCM)</title>
			<author fullname="D. Whiting" initials="D" surname="Whiting"/>
			<author fullname="R. Housley" initials="R" surname="Housley"/>
			<author fullname="N. Ferguson" initials="N" surname="Ferguson"/>
			<date month="September" year="2003"/>
			<abstract>
			<t indent="0">Counter with CBC-MAC (CCM) is a generic authenticate
			d encryption block cipher mode. CCM is defined for use with 128-bit block ciphe
			rs, such as the Advanced Encryption Standard (AES).</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="3610"/>
			<seriesInfo name="DOI" value="10.17487/RFC3610"/>
			</reference>
			<reference anchor="RFC5869" target="https://www.rfc-editor.org/info/rfc5
			869" quoteTitle="true" derivedAnchor="RFC5869">
			<front>
			<title>HMAC-based Extract-and-Expand Key Derivation Function (HKDF)<
			/title>
			<author fullname="H. Krawczyk" initials="H" surname="Krawczyk"/>
			<author fullname="P. Eronen" initials="P" surname="Eronen"/>
			<date month="May" year="2010"/>
			<abstract>
			<t indent="0">This document specifies a simple Hashed Message Auth
			entication Code (HMAC)-based key derivation function (HKDF), which can be used a
			s a building block in various protocols and applications. The key derivation fu
			nction (KDF) is intended to support a wide range of applications and requirement
			s, and is conservative in its use of cryptographic hash functions. This documen
			t is not an Internet Standards Track specification; it is published for informat
			ional purposes.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="5869"/>
			<seriesInfo name="DOI" value="10.17487/RFC5869"/>
			</reference>
			<reference anchor="RFC6090" target="https://www.rfc-editor.org/info/rfc6
			090" quoteTitle="true" derivedAnchor="RFC6090">
			<front>
			<title>Fundamental Elliptic Curve Cryptography Algorithms</title>
			<author fullname="D. McGrew" initials="D" surname="McGrew"/>
			<author fullname="K. Igoe" initials="K" surname="Igoe"/>
			<author fullname="M. Salter" initials="M" surname="Salter"/>
			<date month="February" year="2011"/>
			<abstract>
			<t indent="0">This note describes the fundamental algorithms of El
			liptic Curve Cryptography (ECC) as they were defined in some seminal references
			from 1994 and earlier. These descriptions may be useful for implementing the fu
			ndamental algorithms without using any of the specialized methods that were deve
			loped in following years. Only elliptic curves defined over fields of character
			istic greater than three are in scope; these curves are those used in Suite B.
			This document is not an Internet Standards Track specification; it is published
			for informational purposes.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="6090"/>
			<seriesInfo name="DOI" value="10.17487/RFC6090"/>
			</reference>
			<reference anchor="RFC6979" target="https://www.rfc-editor.org/info/rfc6
			979" quoteTitle="true" derivedAnchor="RFC6979">
			<front>
			<title>Deterministic Usage of the Digital Signature Algorithm (DSA)
			and Elliptic Curve Digital Signature Algorithm (ECDSA)</title>
			<author fullname="T. Pornin" initials="T" surname="Pornin"/>
			<date month="August" year="2013"/>
			<abstract>
			<t indent="0">This document defines a deterministic digital signat
			ure generation procedure. Such signatures are compatible with standard Digital
			Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA)
			digital signatures and can be processed with unmodified verifiers, which need n
			ot be aware of the procedure described therein. Deterministic signatures retain
			the cryptographic security features associated with digital signatures but can
			be more easily implemented in various environments, since they do not need acces
			s to a source of high-quality randomness.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="6979"/>
			<seriesInfo name="DOI" value="10.17487/RFC6979"/>
			</reference>
			<reference anchor="RFC7748" target="https://www.rfc-editor.org/info/rfc7
			748" quoteTitle="true" derivedAnchor="RFC7748">
			<front>
			<title>Elliptic Curves for Security</title>
			<author fullname="A. Langley" initials="A" surname="Langley"/>
			<author fullname="M. Hamburg" initials="M" surname="Hamburg"/>
			<author fullname="S. Turner" initials="S" surname="Turner"/>
			<date month="January" year="2016"/>
			<abstract>
			<t indent="0">This memo specifies two elliptic curves over prime f
			ields that offer a high level of practical security in cryptographic application
			s, including Transport Layer Security (TLS). These curves are intended to opera
			te at the ~128-bit and ~224-bit security level, respectively, and are generated
			deterministically based on a list of required properties.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="7748"/>
			<seriesInfo name="DOI" value="10.17487/RFC7748"/>
			</reference>
			<reference anchor="RFC8017" target="https://www.rfc-editor.org/info/rfc8
			017" quoteTitle="true" derivedAnchor="RFC8017">
			<front>
			<title>PKCS #1: RSA Cryptography Specifications Version 2.2</title>
			<author fullname="K. Moriarty" initials="K" role="editor" surname="M
			oriarty"/>
			<author fullname="B. Kaliski" initials="B" surname="Kaliski"/>
			<author fullname="J. Jonsson" initials="J" surname="Jonsson"/>
			<author fullname="A. Rusch" initials="A" surname="Rusch"/>
			<date month="November" year="2016"/>
			<abstract>
			<t indent="0">This document provides recommendations for the imple
			mentation of public-key cryptography based on the RSA algorithm, covering crypto
			graphic primitives, encryption schemes, signature schemes with appendix, and ASN
			.1 syntax for representing keys and for identifying the schemes.</t>
			<t indent="0">This document represents a republication of PKCS #1
			v2.2 from RSA Laboratories' Public-Key Cryptography Standards (PKCS) series. By
			publishing this RFC, change control is transferred to the IETF.</t>
			<t indent="0">This document also obsoletes RFC 3447.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8017"/>
			<seriesInfo name="DOI" value="10.17487/RFC8017"/>
			</reference>
			<reference anchor="RFC8032" target="https://www.rfc-editor.org/info/rfc8
			032" quoteTitle="true" derivedAnchor="RFC8032">
			<front>
			<title>Edwards-Curve Digital Signature Algorithm (EdDSA)</title>
			<author fullname="S. Josefsson" initials="S" surname="Josefsson"/>
			<author fullname="I. Liusvaara" initials="I" surname="Liusvaara"/>
			<date month="January" year="2017"/>
			<abstract>
			<t indent="0">This document describes elliptic curve signature sch
			eme Edwards-curve Digital Signature Algorithm (EdDSA). The algorithm is instant
			iated with recommended parameters for the edwards25519 and edwards448 curves. A
			n example implementation and test vectors are provided.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8032"/>
			<seriesInfo name="DOI" value="10.17487/RFC8032"/>
			</reference>
			<reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8
			174" quoteTitle="true" derivedAnchor="RFC8174">
			<front>
			<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
			tle>
			<author fullname="B. Leiba" initials="B" surname="Leiba"/>
			<date month="May" year="2017"/>
			<abstract>
			<t indent="0">RFC 2119 specifies common key words that may be used
			in protocol specifications. This document aims to reduce the ambiguity by clar
			ifying that only UPPERCASE usage of the key words have the defined special meani
			ngs.</t>
			</abstract>
			</front>
			<seriesInfo name="BCP" value="14"/>
			<seriesInfo name="RFC" value="8174"/>
			<seriesInfo name="DOI" value="10.17487/RFC8174"/>
			</reference>
			<reference anchor="RFC8439" target="https://www.rfc-editor.org/info/rfc8
			439" quoteTitle="true" derivedAnchor="RFC8439">
			<front>
			<title>ChaCha20 and Poly1305 for IETF Protocols</title>
			<author fullname="Y. Nir" initials="Y" surname="Nir"/>
			<author fullname="A. Langley" initials="A" surname="Langley"/>
			<date month="June" year="2018"/>
			<abstract>
			<t indent="0">This document defines the ChaCha20 stream cipher as
			well as the use of the Poly1305 authenticator, both as stand-alone algorithms an
			d as a "combined mode", or Authenticated Encryption with Associated Data (AEAD)
			algorithm.</t>
			<t indent="0">RFC 7539, the predecessor of this document, was mean
			t to serve as a stable reference and an implementation guide. It was a product o
			f the Crypto Forum Research Group (CFRG). This document merges the errata filed
			against RFC 7539 and adds a little text to the Security Considerations section.<
			/t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8439"/>
			<seriesInfo name="DOI" value="10.17487/RFC8439"/>
			</reference>
			<reference anchor="RFC9052" target="https://www.rfc-editor.org/info/rfc9
			052" quoteTitle="true" derivedAnchor="RFC9052">
			<front>
			<title>CBOR Object Signing and Encryption (COSE): Structures and Pro
			cess</title>
			<author initials="J" surname="Schaad">
			<organization showOnFrontPage="true"/>
			</author>
			<date month="August" year="2022"/>
			</front>
			<seriesInfo name="STD" value="96"/>
			<seriesInfo name="RFC" value="9052"/>
			<seriesInfo name="DOI" value="10.17487/RFC9052"/>
			</reference>
			<reference anchor="SEC1" target="https://www.secg.org/sec1-v2.pdf" quote
			Title="true" derivedAnchor="SEC1">
	<front>		<front>
	<title>SEC 1: Elliptic Curve Cryptography</title>		<title>SEC 1: Elliptic Curve Cryptography</title>
	<author>		<author>
	<organization>Certicom Research</organization>		<organization showOnFrontPage="true">Certicom Research</organizati on>
	</author>		</author>
	<date year="2009" month="May"/>		<date year="2009" month="May"/>
	</front>		</front>
			<refcontent>Standards for Efficient Cryptography</refcontent>
			</reference>
			<reference anchor="STD94" target="https://www.rfc-editor.org/info/std94"
			quoteTitle="true" derivedAnchor="STD94">
			<front>
			<title>Concise Binary Object Representation (CBOR)</title>
			<author initials="C." surname="Bormann" fullname="C. Bormann">
			<organization showOnFrontPage="true"/>
			</author>
			<author initials="P." surname="Hoffman" fullname="P. Hoffman">
			<organization showOnFrontPage="true"/>
			</author>
			<date year="2020" month="December"/>
			</front>
			<seriesInfo name="STD" value="94"/>
			<seriesInfo name="RFC" value="8949"/>
	</reference>		</reference>
	<xi:include href="reference.RFC.8032.xml"/>
	<xi:include href="reference.RFC.8017.xml"/>
	</references>		</references>
	<references>		<references pn="section-12.2">
	<name>Informative References</name>		<name slugifiedName="name-informative-references">Informative References
	<xi:include href="reference.RFC.8126.xml"/>		</name>
	<xi:include href="reference.RFC.8610.xml"/>		<reference anchor="I-D.mattsson-cfrg-det-sigs-with-noise" quoteTitle="tr
	<xi:include href="reference.RFC.4231.xml"/>		ue" target="https://datatracker.ietf.org/doc/html/draft-mattsson-cfrg-det-sigs-w
	<xi:include href="reference.RFC.4493.xml"/>		ith-noise-04" derivedAnchor="CFRG-DET-SIGS">
	<xi:include href="reference.RFC.5116.xml"/>
	<xi:include href="reference.RFC.5480.xml"/>
	<xi:include href="reference.RFC.6151.xml"/>
	<!-- <xi:include href="bibxml9/reference.STD.0090.xml"/> -->
	<referencegroup anchor="STD90" target="https://www.rfc-editor.org/info/std90">
	<!-- reference.RFC.8259.xml -->
	<reference anchor="RFC8259" target="https://www.rfc-editor.org/info/rfc8259">
	<front>
	<title>
	The JavaScript Object Notation (JSON) Data Interchange Format
	</title>
	<author initials="T." surname="Bray" fullname="T. Bray" role="editor">
	<organization/>
	</author>
	<date year="2017" month="December"/>
	<abstract>
	<t>
	JavaScript Object Notation (JSON) is a lightweight, text-based, language-indepen
	dent data interchange format. It was derived from the ECMAScript Programming Lan
	guage Standard. JSON defines a small set of formatting rules for the portable re
	presentation of structured data.
	</t>
	<t>
	This document removes inconsistencies with other specifications of JSON, repairs
	specification errors, and offers experience-based interoperability guidance.
	</t>
	</abstract>
	</front>
	<seriesInfo name="STD" value="90"/>
	<seriesInfo name="RFC" value="8259"/>
	<seriesInfo name="DOI" value="10.17487/RFC8259"/>
	</reference>
	</referencegroup>
	<xi:include href="reference.RFC.7252.xml"/>
	<xi:include href="reference.RFC.7518.xml"/>
	<xi:include href="reference.RFC.8152.xml"/>
	<xi:include href="reference.RFC.8551.xml"/>
	<xi:include href="reference.RFC.8230.xml"/>
	<xi:include href="reference.I-D.ietf-core-oscore-groupcomm.xml"/>
	<xi:include href="reference.I-D.ietf-cose-hash-sig.xml"/>
	<reference anchor="SP800-38d" target="https://nvlpubs.nist.gov/nistpubs/
	Legacy/SP/nistspecialpublication800-38d.pdf">
	<front>		<front>
	<title>Recommendation for Block Cipher Modes of Operation: Galois/C		<title>Deterministic ECDSA and EdDSA Signatures with Additional Rand
	ounter Mode (GCM) and GMAC</title>		omness</title>
	<seriesInfo name="NIST Special Publication 800-38D" value=""/>		<author fullname="John Preuß Mattsson">
	<author initials="M." surname="Dworkin"/>		<organization showOnFrontPage="true">Ericsson</organization>
	<date year="2007" month="Nov"/>		</author>
			<author fullname="Erik Thormarker">
			<organization showOnFrontPage="true">Ericsson</organization>
			</author>
			<author fullname="Sini Ruohomaa">
			<organization showOnFrontPage="true">Ericsson</organization>
			</author>
			<date month="February" day="15" year="2022"/>
			<abstract>
			<t indent="0"> Deterministic elliptic-curve signatures such as d
			eterministic ECDSA
			and EdDSA have gained popularity over randomized ECDSA as their
			security do not depend on a source of high-quality randomness.
			Recent research has however found that implementations of these
			signature algorithms may be vulnerable to certain side-channel and
			fault injection attacks due to their determinism. One countermeasure
			to such attacks is to re-add randomness to the otherwise
			deterministic calculation of the per-message secret number. This
			document updates RFC 6979 and RFC 8032 to recommend constructions
			with additional randomness for deployments where side-channel attacks
			and fault injection attacks are a concern. The updates are invisible
			to the validator of the signature and compatible with existing ECDSA
			and EdDSA validators.
			</t>
			</abstract>
	</front>		</front>
			<seriesInfo name="Internet-Draft" value="draft-mattsson-cfrg-det-sigs-
			with-noise-04"/>
			<format type="TXT" target="https://www.ietf.org/archive/id/draft-matts
			son-cfrg-det-sigs-with-noise-04.txt"/>
			<refcontent>Work in Progress</refcontent>
	</reference>		</reference>
			<reference anchor="I-D.ietf-cose-countersign" quoteTitle="true" target="
			https://datatracker.ietf.org/doc/html/draft-ietf-cose-countersign-08" derivedAnc
			hor="COUNTERSIGN">
			<front>
			<title>CBOR Object Signing and Encryption (COSE): Countersignatures<
			/title>
			<author fullname="Jim Schaad">
			<organization showOnFrontPage="true">August Cellars</organization>
			</author>
			<author fullname="Russ Housley">
			<organization showOnFrontPage="true">Vigil Security, LLC</organiza
			tion>
			</author>
			<date month="August" day="22" year="2022"/>
			<abstract>
			<t indent="0"> Concise Binary Object Representation (CBOR) is a
			data format designed
			for small code size and small message size. CBOR Object Signing and
			Encryption (COSE) defines a set of security services for CBOR. This
			document defines a countersignature algorithm along with the needed
			header parameters and CBOR tags for COSE. This document updates RFC
			INSERT the number assigned to [I-D.ietf-cose-rfc8152bis-struct].
	<reference anchor="SP800-56A" target="http://nvlpubs.nist.gov/nistpubs/S		</t>
	pecialPublications/NIST.SP.800-56Ar2.pdf">		</abstract>
			</front>
			<seriesInfo name="Internet-Draft" value="draft-ietf-cose-countersign-0
			8"/>
			<format type="TXT" target="https://www.ietf.org/archive/id/draft-ietf-
			cose-countersign-08.txt"/>
			<refcontent>Work in Progress</refcontent>
			</reference>
			<reference anchor="GitHub-Examples" target="https://github.com/cose-wg/E
			xamples" quoteTitle="true" derivedAnchor="GitHub-Examples">
			<front>
			<title>GitHub Examples of COSE</title>
			<author/>
			<date month="June" day="3" year="2020"/>
			</front>
			<refcontent>commit 3221310</refcontent>
			</reference>
			<reference anchor="HKDF" target="https://eprint.iacr.org/2010/264.pdf" q
			uoteTitle="true" derivedAnchor="HKDF">
			<front>
			<title>Cryptographic Extraction and Key Derivation: The HKDF Scheme<
			/title>
			<author initials="H." surname="Krawczyk">
			<organization showOnFrontPage="true">IBM T.J. Watson Research Cent
			er</organization>
			</author>
			<date year="2010"/>
			</front>
			</reference>
			<reference anchor="I-D.ietf-core-oscore-groupcomm" quoteTitle="true" tar
			get="https://datatracker.ietf.org/doc/html/draft-ietf-core-oscore-groupcomm-14"
			derivedAnchor="OSCORE-GROUPCOMM">
			<front>
			<title>Group OSCORE - Secure Group Communication for CoAP</title>
			<author fullname="Marco Tiloca">
			<organization showOnFrontPage="true">RISE AB</organization>
			</author>
			<author fullname="Göran Selander">
			<organization showOnFrontPage="true">Ericsson AB</organization>
			</author>
			<author fullname="Francesca Palombini">
			<organization showOnFrontPage="true">Ericsson AB</organization>
			</author>
			<author fullname="John Preuss Mattsson">
			<organization showOnFrontPage="true">Ericsson AB</organization>
			</author>
			<author fullname="Jiye Park">
			<organization showOnFrontPage="true">Universitaet Duisburg-Essen</
			organization>
			</author>
			<date month="March" day="7" year="2022"/>
			<abstract>
			<t indent="0"> This document defines Group Object Security for C
			onstrained RESTful
			Environments (Group OSCORE), providing end-to-end security of CoAP
			messages exchanged between members of a group, e.g., sent over IP
			multicast. In particular, the described approach defines how OSCORE
			is used in a group communication setting to provide source
			authentication for CoAP group requests, sent by a client to multiple
			servers, and for protection of the corresponding CoAP responses.
			Group OSCORE also defines a pairwise mode where each member of the
			group can efficiently derive a symmetric pairwise key with any other
			member of the group for pairwise OSCORE communication.
			</t>
			</abstract>
			</front>
			<seriesInfo name="Internet-Draft" value="draft-ietf-core-oscore-groupc
			omm-14"/>
			<format type="TXT" target="https://www.ietf.org/archive/id/draft-ietf-
			core-oscore-groupcomm-14.txt"/>
			<refcontent>Work in Progress</refcontent>
			</reference>
			<reference anchor="RFC4231" target="https://www.rfc-editor.org/info/rfc4
			231" quoteTitle="true" derivedAnchor="RFC4231">
			<front>
			<title>Identifiers and Test Vectors for HMAC-SHA-224, HMAC-SHA-256,
			HMAC-SHA-384, and HMAC-SHA-512</title>
			<author fullname="M. Nystrom" initials="M" surname="Nystrom"/>
			<date month="December" year="2005"/>
			<abstract>
			<t indent="0">This document provides test vectors for the HMAC-SHA
			-224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 message authentication scheme
			s. It also provides ASN.1 object identifiers and Uniform Resource Identifiers (
			URIs) to identify use of these schemes in protocols. The test vectors provided
			in this document may be used for conformance testing. [STANDARDS-TRACK]</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="4231"/>
			<seriesInfo name="DOI" value="10.17487/RFC4231"/>
			</reference>
			<reference anchor="RFC4493" target="https://www.rfc-editor.org/info/rfc4
			493" quoteTitle="true" derivedAnchor="RFC4493">
			<front>
			<title>The AES-CMAC Algorithm</title>
			<author fullname="JH. Song" initials="JH" surname="Song"/>
			<author fullname="R. Poovendran" initials="R" surname="Poovendran"/>
			<author fullname="J. Lee" initials="J" surname="Lee"/>
			<author fullname="T. Iwata" initials="T" surname="Iwata"/>
			<date month="June" year="2006"/>
			<abstract>
			<t indent="0">The National Institute of Standards and Technology (
			NIST) has recently specified the Cipher-based Message Authentication Code (CMAC)
			, which is equivalent to the One-Key CBC MAC1 (OMAC1) submitted by Iwata and Kur
			osawa. This memo specifies an authentication algorithm based on CMAC with the 1
			28-bit Advanced Encryption Standard (AES). This new authentication algorithm is
			named AES-CMAC. The purpose of this document is to make the AES-CMAC algorithm
			conveniently available to the Internet Community. This memo provides informati
			on for the Internet community.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="4493"/>
			<seriesInfo name="DOI" value="10.17487/RFC4493"/>
			</reference>
			<reference anchor="RFC5116" target="https://www.rfc-editor.org/info/rfc5
			116" quoteTitle="true" derivedAnchor="RFC5116">
			<front>
			<title>An Interface and Algorithms for Authenticated Encryption</tit
			le>
			<author fullname="D. McGrew" initials="D" surname="McGrew"/>
			<date month="January" year="2008"/>
			<abstract>
			<t indent="0">This document defines algorithms for Authenticated E
			ncryption with Associated Data (AEAD), and defines a uniform interface and a reg
			istry for such algorithms. The interface and registry can be used as an applica
			tion-independent set of cryptoalgorithm suites. This approach provides advantag
			es in efficiency and security, and promotes the reuse of crypto implementations.
			[STANDARDS-TRACK]</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="5116"/>
			<seriesInfo name="DOI" value="10.17487/RFC5116"/>
			</reference>
			<reference anchor="RFC5480" target="https://www.rfc-editor.org/info/rfc5
			480" quoteTitle="true" derivedAnchor="RFC5480">
			<front>
			<title>Elliptic Curve Cryptography Subject Public Key Information</t
			itle>
			<author fullname="S. Turner" initials="S" surname="Turner"/>
			<author fullname="D. Brown" initials="D" surname="Brown"/>
			<author fullname="K. Yiu" initials="K" surname="Yiu"/>
			<author fullname="R. Housley" initials="R" surname="Housley"/>
			<author fullname="T. Polk" initials="T" surname="Polk"/>
			<date month="March" year="2009"/>
			<abstract>
			<t indent="0">This document specifies the syntax and semantics for
			the Subject Public Key Information field in certificates that support Elliptic
			Curve Cryptography. This document updates Sections 2.3.5 and 5, and the ASN.1 m
			odule of "Algorithms and Identifiers for the Internet X.509 Public Key Infrastru
			cture Certificate and Certificate Revocation List (CRL) Profile", RFC 3279. [STA
			NDARDS-TRACK]</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="5480"/>
			<seriesInfo name="DOI" value="10.17487/RFC5480"/>
			</reference>
			<reference anchor="RFC6151" target="https://www.rfc-editor.org/info/rfc6
			151" quoteTitle="true" derivedAnchor="RFC6151">
			<front>
			<title>Updated Security Considerations for the MD5 Message-Digest an
			d the HMAC-MD5 Algorithms</title>
			<author fullname="S. Turner" initials="S" surname="Turner"/>
			<author fullname="L. Chen" initials="L" surname="Chen"/>
			<date month="March" year="2011"/>
			<abstract>
			<t indent="0">This document updates the security considerations fo
			r the MD5 message digest algorithm. It also updates the security considerations
			for HMAC-MD5. This document is not an Internet Standards Track specification;
			it is published for informational purposes.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="6151"/>
			<seriesInfo name="DOI" value="10.17487/RFC6151"/>
			</reference>
			<reference anchor="RFC7252" target="https://www.rfc-editor.org/info/rfc7
			252" quoteTitle="true" derivedAnchor="RFC7252">
			<front>
			<title>The Constrained Application Protocol (CoAP)</title>
			<author fullname="Z. Shelby" initials="Z" surname="Shelby"/>
			<author fullname="K. Hartke" initials="K" surname="Hartke"/>
			<author fullname="C. Bormann" initials="C" surname="Bormann"/>
			<date month="June" year="2014"/>
			<abstract>
			<t indent="0">The Constrained Application Protocol (CoAP) is a spe
			cialized web transfer protocol for use with constrained nodes and constrained (e
			.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers wit
			h small amounts of ROM and RAM, while constrained networks such as IPv6 over Low
			-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error r
			ates and a typical throughput of 10s of kbit/s. The protocol is designed for mac
			hine- to-machine (M2M) applications such as smart energy and building automation
			.</t>
			<t indent="0">CoAP provides a request/response interaction model b
			etween application endpoints, supports built-in discovery of services and resour
			ces, and includes key concepts of the Web such as URIs and Internet media types.
			CoAP is designed to easily interface with HTTP for integration with the Web whi
			le meeting specialized requirements such as multicast support, very low overhead
			, and simplicity for constrained environments.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="7252"/>
			<seriesInfo name="DOI" value="10.17487/RFC7252"/>
			</reference>
			<reference anchor="RFC7518" target="https://www.rfc-editor.org/info/rfc7
			518" quoteTitle="true" derivedAnchor="RFC7518">
			<front>
			<title>JSON Web Algorithms (JWA)</title>
			<author fullname="M. Jones" initials="M" surname="Jones"/>
			<date month="May" year="2015"/>
			<abstract>
			<t indent="0">This specification registers cryptographic algorithm
			s and identifiers to be used with the JSON Web Signature (JWS), JSON Web Encrypt
			ion (JWE), and JSON Web Key (JWK) specifications. It defines several IANA regis
			tries for these identifiers.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="7518"/>
			<seriesInfo name="DOI" value="10.17487/RFC7518"/>
			</reference>
			<reference anchor="RFC8126" target="https://www.rfc-editor.org/info/rfc8
			126" quoteTitle="true" derivedAnchor="RFC8126">
			<front>
			<title>Guidelines for Writing an IANA Considerations Section in RFCs
			</title>
			<author fullname="M. Cotton" initials="M" surname="Cotton"/>
			<author fullname="B. Leiba" initials="B" surname="Leiba"/>
			<author fullname="T. Narten" initials="T" surname="Narten"/>
			<date month="June" year="2017"/>
			<abstract>
			<t indent="0">Many protocols make use of points of extensibility t
			hat use constants to identify various protocol parameters. To ensure that the va
			lues in these fields do not have conflicting uses and to promote interoperabilit
			y, their allocations are often coordinated by a central record keeper. For IETF
			protocols, that role is filled by the Internet Assigned Numbers Authority (IANA)
			.</t>
			<t indent="0">To make assignments in a given registry prudently, g
			uidance describing the conditions under which new values should be assigned, as
			well as when and how modifications to existing values can be made, is needed. Th
			is document defines a framework for the documentation of these guidelines by spe
			cification authors, in order to assure that the provided guidance for the IANA C
			onsiderations is clear and addresses the various issues that are likely in the o
			peration of a registry.</t>
			<t indent="0">This is the third edition of this document; it obsol
			etes RFC 5226.</t>
			</abstract>
			</front>
			<seriesInfo name="BCP" value="26"/>
			<seriesInfo name="RFC" value="8126"/>
			<seriesInfo name="DOI" value="10.17487/RFC8126"/>
			</reference>
			<reference anchor="RFC8152" target="https://www.rfc-editor.org/info/rfc8
			152" quoteTitle="true" derivedAnchor="RFC8152">
			<front>
			<title>CBOR Object Signing and Encryption (COSE)</title>
			<author fullname="J. Schaad" initials="J" surname="Schaad"/>
			<date month="July" year="2017"/>
			<abstract>
			<t indent="0">Concise Binary Object Representation (CBOR) is a dat
			a format designed for small code size and small message size. There is a need f
			or the ability to have basic security services defined for this data format. Th
			is document defines the CBOR Object Signing and Encryption (COSE) protocol. Thi
			s specification describes how to create and process signatures, message authenti
			cation codes, and encryption using CBOR for serialization. This specification a
			dditionally describes how to represent cryptographic keys using CBOR.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8152"/>
			<seriesInfo name="DOI" value="10.17487/RFC8152"/>
			</reference>
			<reference anchor="RFC8230" target="https://www.rfc-editor.org/info/rfc8
			230" quoteTitle="true" derivedAnchor="RFC8230">
			<front>
			<title>Using RSA Algorithms with CBOR Object Signing and Encryption
			(COSE) Messages</title>
			<author fullname="M. Jones" initials="M" surname="Jones"/>
			<date month="September" year="2017"/>
			<abstract>
			<t indent="0">The CBOR Object Signing and Encryption (COSE) specif
			ication defines cryptographic message encodings using Concise Binary Object Repr
			esentation (CBOR). This specification defines algorithm encodings and represent
			ations enabling RSA algorithms to be used for COSE messages. Encodings are spec
			ified for the use of RSA Probabilistic Signature Scheme (RSASSA-PSS) signatures,
			RSA Encryption Scheme - Optimal Asymmetric Encryption Padding (RSAES-OAEP) encr
			yption, and RSA keys.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8230"/>
			<seriesInfo name="DOI" value="10.17487/RFC8230"/>
			</reference>
			<reference anchor="RFC8446" target="https://www.rfc-editor.org/info/rfc8
			446" quoteTitle="true" derivedAnchor="RFC8446">
			<front>
			<title>The Transport Layer Security (TLS) Protocol Version 1.3</titl
			e>
			<author fullname="E. Rescorla" initials="E" surname="Rescorla"/>
			<date month="August" year="2018"/>
			<abstract>
			<t indent="0">This document specifies version 1.3 of the Transport
			Layer Security (TLS) protocol. TLS allows client/server applications to communi
			cate over the Internet in a way that is designed to prevent eavesdropping, tampe
			ring, and message forgery.</t>
			<t indent="0">This document updates RFCs 5705 and 6066, and obsole
			tes RFCs 5077, 5246, and 6961. This document also specifies new requirements for
			TLS 1.2 implementations.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8446"/>
			<seriesInfo name="DOI" value="10.17487/RFC8446"/>
			</reference>
			<reference anchor="RFC8551" target="https://www.rfc-editor.org/info/rfc8
			551" quoteTitle="true" derivedAnchor="RFC8551">
			<front>
			<title>Secure/Multipurpose Internet Mail Extensions (S/MIME) Version
			4.0 Message Specification</title>
			<author fullname="J. Schaad" initials="J" surname="Schaad"/>
			<author fullname="B. Ramsdell" initials="B" surname="Ramsdell"/>
			<author fullname="S. Turner" initials="S" surname="Turner"/>
			<date month="April" year="2019"/>
			<abstract>
			<t indent="0">This document defines Secure/Multipurpose Internet M
			ail Extensions (S/MIME) version 4.0. S/MIME provides a consistent way to send a
			nd receive secure MIME data. Digital signatures provide authentication, message
			integrity, and non-repudiation with proof of origin. Encryption provides data
			confidentiality. Compression can be used to reduce data size. This document ob
			soletes RFC 5751.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8551"/>
			<seriesInfo name="DOI" value="10.17487/RFC8551"/>
			</reference>
			<reference anchor="RFC8610" target="https://www.rfc-editor.org/info/rfc8
			610" quoteTitle="true" derivedAnchor="RFC8610">
			<front>
			<title>Concise Data Definition Language (CDDL): A Notational Convent
			ion to Express Concise Binary Object Representation (CBOR) and JSON Data Structu
			res</title>
			<author fullname="H. Birkholz" initials="H" surname="Birkholz"/>
			<author fullname="C. Vigano" initials="C" surname="Vigano"/>
			<author fullname="C. Bormann" initials="C" surname="Bormann"/>
			<date month="June" year="2019"/>
			<abstract>
			<t indent="0">This document proposes a notational convention to ex
			press Concise Binary Object Representation (CBOR) data structures (RFC 7049). I
			ts main goal is to provide an easy and unambiguous way to express structures for
			protocol messages and data formats that use CBOR or JSON.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8610"/>
			<seriesInfo name="DOI" value="10.17487/RFC8610"/>
			</reference>
			<reference anchor="RFC8778" target="https://www.rfc-editor.org/info/rfc8
			778" quoteTitle="true" derivedAnchor="RFC8778">
			<front>
			<title>Use of the HSS/LMS Hash-Based Signature Algorithm with CBOR O
			bject Signing and Encryption (COSE)</title>
			<author fullname="R. Housley" initials="R" surname="Housley"/>
			<date month="April" year="2020"/>
			<abstract>
			<t indent="0">This document specifies the conventions for using th
			e Hierarchical Signature System (HSS) / Leighton-Micali Signature (LMS) hash-bas
			ed signature algorithm with the CBOR Object Signing and Encryption (COSE) syntax
			. The HSS/LMS algorithm is one form of hash-based digital signature; it is desc
			ribed in RFC 8554.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8778"/>
			<seriesInfo name="DOI" value="10.17487/RFC8778"/>
			</reference>
			<reference anchor="RFC9021" target="https://www.rfc-editor.org/info/rfc9
			021" quoteTitle="true" derivedAnchor="RFC9021">
			<front>
			<title>Use of the Walnut Digital Signature Algorithm with CBOR Objec
			t Signing and Encryption (COSE)</title>
			<author fullname="D. Atkins" initials="D" surname="Atkins"/>
			<date month="May" year="2021"/>
			<abstract>
			<t indent="0">This document specifies the conventions for using th
			e Walnut Digital Signature Algorithm (WalnutDSA) for digital signatures with the
			CBOR Object Signing and Encryption (COSE) syntax. WalnutDSA is a lightweight, q
			uantum-resistant signature scheme based on Group Theoretic Cryptography with imp
			lementation and computational efficiency of signature verification in constraine
			d environments, even on 8- and 16-bit platforms.</t>
			<t indent="0">The goal of this publication is to document a way to
			use the lightweight, quantum-resistant WalnutDSA signature algorithm in COSE in
			a way that would allow multiple developers to build compatible implementations.
			As of this publication, the security properties of WalnutDSA have not been eval
			uated by the IETF and its use has not been endorsed by the IETF.</t>
			<t indent="0">WalnutDSA and the Walnut Digital Signature Algorithm
			are trademarks of Veridify Security Inc.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="9021"/>
			<seriesInfo name="DOI" value="10.17487/RFC9021"/>
			</reference>
			<reference anchor="RFC9147" target="https://www.rfc-editor.org/info/rfc9
			147" quoteTitle="true" derivedAnchor="RFC9147">
			<front>
			<title>The Datagram Transport Layer Security (DTLS) Protocol Version
			1.3</title>
			<author fullname="E. Rescorla" initials="E" surname="Rescorla"/>
			<author fullname="H. Tschofenig" initials="H" surname="Tschofenig"/>
			<author fullname="N. Modadugu" initials="N" surname="Modadugu"/>
			<date month="April" year="2022"/>
			<abstract>
			<t indent="0">This document specifies version 1.3 of the Datagram
			Transport Layer Security (DTLS) protocol. DTLS 1.3 allows client/server applicat
			ions to communicate over the Internet in a way that is designed to prevent eaves
			dropping, tampering, and message forgery.</t>
			<t indent="0">The DTLS 1.3 protocol is based on the Transport Laye
			r Security (TLS) 1.3 protocol and provides equivalent security guarantees with t
			he exception of order protection / non-replayability. Datagram semantics of the
			underlying transport are preserved by the DTLS protocol.</t>
			<t indent="0">This document obsoletes RFC 6347.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="9147"/>
			<seriesInfo name="DOI" value="10.17487/RFC9147"/>
			</reference>
			<reference anchor="ROBUST" target="https://eprint.iacr.org/2020/718.pdf"
			quoteTitle="true" derivedAnchor="ROBUST">
			<front>
			<title>Robust Channels: Handling Unreliable Networks in the Record L
			ayers of QUIC and DTLS</title>
			<author initials="M." surname="Fischlin"/>
			<author initials="F." surname="Günther"/>
			<author initials="C." surname="Janson"/>
			<date year="2020" month="Feb"/>
			</front>
			</reference>
			<reference anchor="SP800-38D" target="https://nvlpubs.nist.gov/nistpubs/
			Legacy/SP/nistspecialpublication800-38d.pdf" quoteTitle="true" derivedAnchor="SP
			800-38D">
			<front>
			<title>Recommendation for Block Cipher Modes of Operation: Galois/Co
			unter Mode (GCM) and GMAC</title>
			<seriesInfo name="NIST Special Publication" value="800-38D"/>
			<author initials="M." surname="Dworkin"/>
			<date year="2007" month="November"/>
			</front>
			</reference>
			<reference anchor="SP800-56A" target="https://nvlpubs.nist.gov/nistpubs/
			SpecialPublications/NIST.SP.800-56Ar2.pdf" quoteTitle="true" derivedAnchor="SP80
			0-56A">
	<front>		<front>
	<title>Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography</title>		<title>Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography</title>
	<seriesInfo name="DOI" value="10.6028/NIST.SP.800-56Ar2"/>
	<seriesInfo name="NIST Special Publication 800-56A," value="Revision
	2"/>
	<author initials="E." surname="Barker">		<author initials="E." surname="Barker">
	<organization>U.S. National Institute of Standards and Technology< /organization>		<organization showOnFrontPage="true"/>
	</author>		</author>
	<author initials="L." surname="Chen">		<author initials="L." surname="Chen">
	<organization>U.S. National Institute of Standards and Technology< /organization>		<organization showOnFrontPage="true"/>
	</author>		</author>
	<author initials="A." surname="Roginsky">		<author initials="A." surname="Roginsky">
	<organization>U.S. National Institute of Standards and Technology< /organization>		<organization showOnFrontPage="true"/>
	</author>		</author>
	<author initials="M." surname="Smid">		<author initials="A." surname="Vassilev">
	<organization>Orion Security Solutions, Inc.</organization>		<organization showOnFrontPage="true"/>
	</author>		</author>
	<date year="2013" month="May"/>		<author initials="R." surname="Davis">
			<organization showOnFrontPage="true"/>
			</author>
			<date year="2018" month="April"/>
	</front>		</front>
			<seriesInfo name="DOI" value="10.6028/NIST.SP.800-56Ar3"/>
			<refcontent>NIST Special Publication 800-56A, Revision 3</refcontent>
	</reference>		</reference>
	<reference anchor="GitHub-Examples" target="https://github.com/cose-wg/E xamples">		<reference anchor="STD90" target="https://www.rfc-editor.org/info/std90" quoteTitle="true" derivedAnchor="STD90">
	<front>		<front>
	<title>GitHub Examples of COSE</title>		<title>The JavaScript Object Notation (JSON) Data Interchange Format
	<author/>		</title>
			<author initials="T." surname="Bray" fullname="Tim Bray" role="edito
			r">
			<organization showOnFrontPage="true"/>
			</author>
			<date month="December" year="2017"/>
	</front>		</front>
			<seriesInfo name="STD" value="90"/>
			<seriesInfo name="RFC" value="8259"/>
	</reference>		</reference>
	<xi:include href="reference.I-D.mattsson-cfrg-det-sigs-with-noise.xml"/>
	<reference anchor="HKDF" target="https://eprint.iacr.org/2010/264.pdf">
	<front>
	<title>Cryptographic Extraction and Key Derivation: The HKDF Scheme</t
	itle>
	<author initials="H." surname="Krawczyk">
	<organization>IBM T.J. Watson Research Center</organization>
	</author>
	<date year="2010"/>
	</front>
	</reference>
	<reference anchor="ROBUST" target="https://www.felixguenther.info/docs/QUI
	P2020_RobustChannels.pdf">
	<front>
	<title>Robust Channels: Handling Unreliable Networks in the Record Lay
	ers of QUIC and DTLS</title>
	<author initials="M." surname="Fischlin"/>
	<author initials="F." surname="Günther"/>
	<author initials="C." surname="Janson"/>
	<date year="2020" month="Feb"/>
	</front>
	</reference>
	<xi:include href="reference.I-D.ietf-quic-tls.xml"/>
	</references>		</references>
	</references>		</references>
	<section numbered="false">		<section numbered="false" removeInRFC="false" toc="include" pn="section-appe
			ndix.a">
			<name slugifiedName="name-acknowledgments">Acknowledgments</name>
			<t indent="0" pn="section-appendix.a-1">This document is a product of the
			COSE Working Group of the IETF. </t>
			<t indent="0" pn="section-appendix.a-2">The following individuals are to b
			lame for getting me started on this
			project in the first place: <contact fullname="Richard Barnes"/>,
			<contact fullname="Matt Miller"/>, and <contact fullname="Martin Tho
			mson"/>. </t>
			<t indent="0" pn="section-appendix.a-3">The initial draft version of the s
			pecification was based to some degree on
			the outputs of the JOSE and S/MIME Working Groups. </t>
			<t indent="0" pn="section-appendix.a-4">The following individuals provided
			input into the final form of the
			document: <contact fullname="Carsten Bormann"/>, <contact fullname="John
			Bradley"/>, <contact fullname="Brian Campbell"/>, <contact fullname="Michae
			l B. Jones"/>, <contact fullname="Ilari Liusvaara"/>,
			<contact fullname="Francesca Palombini"/>, <contact fullname="Ludwig
			Seitz"/>, and <contact fullname="Göran Selander"/>. </t>
			</section>
			<section anchor="authors-addresses" numbered="false" removeInRFC="false" toc
			="include" pn="section-appendix.b">
			<name slugifiedName="name-authors-address">Author's Address</name>
			<author initials="J." surname="Schaad" fullname="Jim Schaad">
			<organization showOnFrontPage="true">August Cellars</organization>
			<address>
	<name>Acknowledgments</name>		</address>
	<t>This document is a product of the COSE working group of the IETF. </t>		</author>
	<t>The following individuals are to blame for getting me started on this p
	roject in the first place: Richard Barnes, Matt Miller, and Martin Thomson. </t
	>
	<t>The initial version of the specification was based to some degree on th
	e outputs of the JOSE and S/MIME working groups. </t>
	<t>The following individuals provided input into the final form of the doc
	ument: Carsten Bormann, John Bradley, Brain Campbell, Michael B. Jones, Ilari Li
	usvaara, Francesca Palombini, Ludwig Seitz, and Göran Selander. </t>
	</section>		</section>
	</back>		</back>
	</rfc>		</rfc>
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