Diff: rfc9449.original.xml

	rfc9449.original.xml	rfc9449.xml

	<?xml version="1.0" encoding="utf-8"?>	<?xml version="1.0" encoding="UTF-8"?>
	<!-- name="GENERATOR" content="github.com/mmarkdown/mmark Mmark Markdown Process
	or - mmark.miek.nl" -->	<!DOCTYPE rfc [
	<rfc version="3" ipr="trust200902" docName="draft-ietf-oauth-dpop-16" submission	<!ENTITY nbsp " ">
	Type="IETF" category="std" xml:lang="en" xmlns:xi="http://www.w3.org/2001/XInclu	<!ENTITY zwsp "">
	de" indexInclude="true" consensus="true">	<!ENTITY nbhy "‑">
		<!ENTITY wj "⁠">
		]>

		<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft
		-ietf-oauth-dpop-16" number="9449" submissionType="IETF" category="std"
		consensus="true" xml:lang="en" tocInclude="true" sortRefs="true" symRefs="true"
		updates="" obsoletes="" version="3">

	<front>	<front>

	<title abbrev="OAuth DPoP">OAuth 2.0 Demonstrating Proof-of-Possession at the Ap	<title abbrev="OAuth DPoP">OAuth 2.0 Demonstrating Proof of Possession (DPoP)</t
	plication Layer (DPoP)</title><seriesInfo value="draft-ietf-oauth-dpop-16" strea	itle>
	m="IETF" status="standard" name="Internet-Draft"></seriesInfo>	<seriesInfo name="RFC" value="9449"/>

	<author initials="D." surname="Fett" fullname="Daniel Fett"><organization>Authle te</organization><address><postal><street></street>	<author initials="D." surname="Fett" fullname="Daniel Fett"><organization>Authle te</organization><address><postal><street></street>
	</postal><email>mail@danielfett.de</email>	</postal><email>mail@danielfett.de</email>

	</address></author><author initials="B." surname="Campbell" fullname="Brian Camp	</address></author>
	bell"><organization>Ping Identity</organization><address><postal><street></stree
	t>	<author initials="B." surname="Campbell" fullname="Brian Campbell"><organization
	</postal><email>bcampbell@pingidentity.com</email>	>Ping Identity</organization><address><postal><street></street>
	</address></author><author initials="J." surname="Bradley" fullname="John Bradle	</postal><email>bcampbell@pingidentity.com</email></address></author>
	y"><organization>Yubico</organization><address><postal><street></street>
		<author initials="J." surname="Bradley" fullname="John Bradley"><organization>Yu
		bico</organization><address><postal><street></street>
	</postal><email>ve7jtb@ve7jtb.com</email>	</postal><email>ve7jtb@ve7jtb.com</email>

	</address></author><author initials="T." surname="Lodderstedt" fullname="Torsten	</address></author>
	Lodderstedt"><organization>yes.com</organization><address><postal><street></str
	eet>	<author initials="T." surname="Lodderstedt" fullname="Torsten Lodderstedt"><orga
	</postal><email>torsten@lodderstedt.net</email>	nization>Tuconic</organization><address><postal><street></street>
	</address></author><author initials="M." surname="Jones" fullname="Michael Jones	</postal><email>torsten@lodderstedt.net</email></address></author>
	"><organization>independent</organization><address><postal><street></street>
		<author initials="M." surname="Jones" fullname="Michael Jones"><organization>Sel
		f-Issued Consulting</organization><address><postal><street></street>
	</postal><email>michael_b_jones@hotmail.com</email>	</postal><email>michael_b_jones@hotmail.com</email>
	<uri>https://self-issued.info/</uri>	<uri>https://self-issued.info/</uri>

	</address></author><author initials="D." surname="Waite" fullname="David Waite">	</address></author>
	<organization>Ping Identity</organization><address><postal><street></street>
		<author initials="D." surname="Waite" fullname="David Waite"><organization>Ping
		Identity</organization><address><postal><street></street>
	</postal><email>david@alkaline-solutions.com</email>	</postal><email>david@alkaline-solutions.com</email>

	</address></author><date/>	</address></author>
	<area>Security</area>
	<workgroup>Web Authorization Protocol</workgroup>	<date year="2023" month="September"/>

		<area>sec</area>
		<workgroup>oauth</workgroup>
	<keyword>security</keyword>	<keyword>security</keyword>
	<keyword>oauth2</keyword>	<keyword>oauth2</keyword>

	<abstract>	<abstract>
	<t>This document describes a mechanism for sender-constraining OAuth 2.0	<t>This document describes a mechanism for sender-constraining OAuth 2.0
	tokens via a proof-of-possession mechanism on the application level.	tokens via a proof-of-possession mechanism on the application level.
	This mechanism allows for the detection of replay attacks with access and refres h	This mechanism allows for the detection of replay attacks with access and refres h
	tokens.</t>	tokens.</t>
	</abstract>	</abstract>

	</front>	</front>

	<middle>	<middle>


	<section anchor="Introduction"><name>Introduction</name>	<section anchor="Introduction"><name>Introduction</name>
	<t>DPoP (for Demonstrating Proof-of-Possession at the Application Layer)	<t>Demonstrating Proof of Possession (DPoP) is an application-level mechanism fo
	is an application-level mechanism for	r
	sender-constraining OAuth <xref target="RFC6749"></xref> access and refresh toke ns. It enables a client to	sender-constraining OAuth <xref target="RFC6749"></xref> access and refresh toke ns. It enables a client to
	prove the possession of a public/private key pair by including	prove the possession of a public/private key pair by including
	a <tt>DPoP</tt> header in an HTTP request. The value of the header is a JSON Web Token	a <tt>DPoP</tt> header in an HTTP request. The value of the header is a JSON Web Token
	(JWT) <xref target="RFC7519"></xref> that enables the authorization	(JWT) <xref target="RFC7519"></xref> that enables the authorization
	server to bind issued tokens to the public part of a client's	server to bind issued tokens to the public part of a client's
	key pair. Recipients of such tokens are then able to verify the binding of the	key pair. Recipients of such tokens are then able to verify the binding of the
	token to the key pair that the client has demonstrated that it holds via	token to the key pair that the client has demonstrated that it holds via
	the <tt>DPoP</tt> header, thereby providing some assurance that the client prese nting	the <tt>DPoP</tt> header, thereby providing some assurance that the client prese nting
	the token also possesses the private key.	the token also possesses the private key.
	In other words, the legitimate presenter of the token is constrained to be	In other words, the legitimate presenter of the token is constrained to be

	the sender that holds and can prove possession of the private part of the	the sender that holds and proves possession of the private part of the
	key pair.</t>	key pair.</t>
	<t>The mechanism specified herein can be used in cases where other	<t>The mechanism specified herein can be used in cases where other
	methods of sender-constraining tokens that utilize elements of the underlying	methods of sender-constraining tokens that utilize elements of the underlying
	secure transport layer, such as <xref target="RFC8705"></xref> or <xref target=" I-D.ietf-oauth-token-binding"></xref>,	secure transport layer, such as <xref target="RFC8705"></xref> or <xref target=" I-D.ietf-oauth-token-binding"></xref>,
	are not available or desirable. For example, due to a sub-par user experience	are not available or desirable. For example, due to a sub-par user experience
	of TLS client authentication in user agents and a lack of support for HTTP token	of TLS client authentication in user agents and a lack of support for HTTP token
	binding, neither mechanism can be used if an OAuth client is an application that	binding, neither mechanism can be used if an OAuth client is an application that
	is dynamically downloaded and executed in a web browser (sometimes referred to a s a	is dynamically downloaded and executed in a web browser (sometimes referred to a s a

	"single-page application"). Applications installed	"single-page application").
	and run directly on a user's device are another example well positioned to benef	Additionally, applications that are installed and run directly
	it	on a user's device are well positioned to benefit from
	from DPoP-bound tokens to guard against misuse of tokens by a compromised	DPoP-bound tokens that guard against the misuse of tokens by
	or malicious resource. Such applications often have dedicated protected storage	a compromised or malicious resource.
		Such applications often have dedicated protected storage
	for cryptographic keys.</t>	for cryptographic keys.</t>
	<t>DPoP can be used to sender-constrain access tokens regardless of the	<t>DPoP can be used to sender-constrain access tokens regardless of the
	client authentication method employed, but DPoP itself is not used for client au thentication.	client authentication method employed, but DPoP itself is not used for client au thentication.
	DPoP can also be used to sender-constrain refresh tokens issued to public client s	DPoP can also be used to sender-constrain refresh tokens issued to public client s
	(those without authentication credentials associated with the <tt>client_id</tt> ).</t>	(those without authentication credentials associated with the <tt>client_id</tt> ).</t>

	<section anchor="conventions-and-terminology"><name>Conventions and Terminology< /name>	<section anchor="conventions-and-terminology"><name>Conventions and Terminology< /name>

	<t>The key words "MUST", "MUST NOT", "REQUIRED", &	<t>
	quot;SHALL", "SHALL	The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQU
	NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",	IRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
	"NOT RECOMMENDED",	NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>
	"MAY", and "OPTIONAL" in this document are to be interpreted	RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
	as	"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
	described in BCP 14 <xref target="RFC2119"></xref> <xref target="RFC8174"></xref	be interpreted as
	> when, and only when, they	described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/>
	appear in all capitals, as shown here.</t>	when, and only when, they appear in all capitals, as shown here.
		</t>
	<t>This specification uses the Augmented Backus-Naur Form (ABNF) notation	<t>This specification uses the Augmented Backus-Naur Form (ABNF) notation
	of <xref target="RFC5234"></xref>.</t>	of <xref target="RFC5234"></xref>.</t>

	<t>This specification uses the terms "access token", "refresh tok	<t>This specification uses the terms "access token", "refresh token",
	en",	"authorization server", "resource server", "authorization endpoint",
	"authorization server", "resource server", "authorizati	"authorization request", "authorization response", "token endpoint",
	on endpoint",	"grant type", "access token request", "access token response",
	"authorization request", "authorization response", "tok	"client", "public client", and "confidential client" defined by "The OAuth 2.0 A
	en endpoint",	uthorization Framework" <xref target="RFC6749"></xref>.</t>
	"grant type", "access token request", "access token res	<t>The terms "request", "response", "header field", and "target URI"
	ponse",
	"client", "public client", and "confidential client&quo
	t; defined by The OAuth 2.0 Authorization Framework <xref target="RFC6749"></xre
	f>.</t>
	<t>The terms "request", "response", "header field"
	, and "target URI"
	are imported from <xref target="RFC9110"></xref>.</t>	are imported from <xref target="RFC9110"></xref>.</t>

	<t>The terms "JOSE" and "JOSE header" are imported from <xre f target="RFC7515"></xref>.</t>	<t>The terms "JOSE" and "JOSE Header" are imported from <xref target="RFC7515">< /xref>.</t>
	<t>This document contains non-normative examples of partial and complete HTTP me ssages.	<t>This document contains non-normative examples of partial and complete HTTP me ssages.
	Some examples use a single trailing backslash to indicate line wrapping for long values, as per <xref target="RFC8792"></xref>.	Some examples use a single trailing backslash to indicate line wrapping for long values, as per <xref target="RFC8792"></xref>.
	The character and leading spaces on wrapped lines are not part of the value.</t>	The character and leading spaces on wrapped lines are not part of the value.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="objective"><name>Objectives</name>	<section anchor="objective"><name>Objectives</name>
	<t>The primary aim of DPoP is to prevent unauthorized or illegitimate	<t>The primary aim of DPoP is to prevent unauthorized or illegitimate
	parties from using leaked or stolen access tokens, by binding a token	parties from using leaked or stolen access tokens, by binding a token
	to a public key upon issuance and requiring that the client proves	to a public key upon issuance and requiring that the client proves
	possession of the corresponding private key when using the token.	possession of the corresponding private key when using the token.
	This constrains the legitimate sender of the token to only the party with	This constrains the legitimate sender of the token to only the party with
	access to the private key and gives the server receiving the token added	access to the private key and gives the server receiving the token added
	assurances that the sender is legitimately authorized to use it.</t>	assurances that the sender is legitimately authorized to use it.</t>
	<t>Access tokens that are sender-constrained via DPoP thus stand in	<t>Access tokens that are sender-constrained via DPoP thus stand in
	contrast to the typical bearer token, which can be used by any party in	contrast to the typical bearer token, which can be used by any party in

	possession of such a token. Although protections generally exist to	possession of such a token. Although protections generally exist to prevent unin
	prevent unintended disclosure of bearer tokens, unforeseen vectors for	tended disclosure of bearer tokens, unforeseen vectors for leakage have occurred
	leakage have occurred due to vulnerabilities and implementation issues	due to vulnerabilities and implementation issues in other layers in the protoco
	in other layers in the protocol or software stack (CRIME <xref target="CRIME"></	l or software stack (see, e.g., Compression Ratio Info-leak Made Easy (CRIME) <x
	xref>, BREACH <xref target="BREACH"></xref>,	ref target="CRIME"></xref>, Browser Reconnaissance and Exfiltration via Adaptive
	Heartbleed <xref target="Heartbleed"></xref>, and the Cloudflare parser bug <xre	Compression of Hypertext (BREACH) <xref target="BREACH"></xref>,
	f target="Cloudbleed"></xref> are some examples).	Heartbleed <xref target="Heartbleed"></xref>, and the Cloudflare parser bug <xre
		f target="Cloudbleed"></xref>).
	There have also been numerous published token theft attacks on OAuth	There have also been numerous published token theft attacks on OAuth

	implementations themselves (<xref target="GitHub.Tokens"></xref> as just one hig h profile example).	implementations themselves (<xref target="GitHub.Tokens"></xref> is just one hig h-profile example).
	DPoP provides a general defense in depth	DPoP provides a general defense in depth
	against the impact of unanticipated token leakage. DPoP is not, however,	against the impact of unanticipated token leakage. DPoP is not, however,

	a substitute for a secure transport and MUST always be used in	a substitute for a secure transport and <bcp14>MUST</bcp14> always be used in
	conjunction with HTTPS.</t>	conjunction with HTTPS.</t>
	<t>The very nature of the typical OAuth protocol interaction	<t>The very nature of the typical OAuth protocol interaction
	necessitates that the client discloses the access token to the	necessitates that the client discloses the access token to the
	protected resources that it accesses. The attacker model	protected resources that it accesses. The attacker model
	in <xref target="I-D.ietf-oauth-security-topics"></xref> describes cases where a	in <xref target="I-D.ietf-oauth-security-topics"></xref> describes cases where a

	protected resource might be counterfeit, malicious or compromised	protected resource might be counterfeit, malicious, or compromised
	and plays received tokens against other protected resources to gain	and plays received tokens against other protected resources to gain

	unauthorized access. Audience restricted access tokens	unauthorized access. Audience-restricted access tokens
	(e.g., using the JWT <xref target="RFC7519"></xref> <tt>aud</tt> claim) can	(e.g., using the JWT <xref target="RFC7519"></xref> <tt>aud</tt> claim) can

	prevent such misuse, however, doing so in practice has proven to be	prevent such misuse. However, doing so in practice has proven to be
	prohibitively cumbersome for many deployments (even despite extensions such as <	prohibitively cumbersome for many deployments (despite extensions such as <xref
	xref target="RFC8707"></xref>).	target="RFC8707"></xref>).
	Sender-constraining access tokens is a more robust and straightforward	Sender-constraining access tokens is a more robust and straightforward

	mechanism to prevent such token replay at a different endpoint and DPoP	mechanism to prevent such token replay at a different endpoint, and DPoP
	is an accessible application layer means of doing so.</t>	is an accessible application-layer means of doing so.</t>
	<t>Due to the potential for cross-site scripting (XSS), browser-based	<t>Due to the potential for cross-site scripting (XSS), browser-based
	OAuth clients bring to bear added considerations with respect to protecting	OAuth clients bring to bear added considerations with respect to protecting
	tokens. The most straightforward XSS-based attack is for an attacker to	tokens. The most straightforward XSS-based attack is for an attacker to
	exfiltrate a token and use it themselves completely independent of the	exfiltrate a token and use it themselves completely independent of the
	legitimate client. A stolen access token is used for protected	legitimate client. A stolen access token is used for protected

	resource access and a stolen refresh token for obtaining new access tokens.	resource access, and a stolen refresh token is used for obtaining new access tok ens.
	If the private key is non-extractable (as is possible with <xref target="W3C.Web CryptoAPI"></xref>),	If the private key is non-extractable (as is possible with <xref target="W3C.Web CryptoAPI"></xref>),
	DPoP renders exfiltrated tokens alone unusable.</t>	DPoP renders exfiltrated tokens alone unusable.</t>
	<t>XSS vulnerabilities also allow an attacker to execute code in the context of	<t>XSS vulnerabilities also allow an attacker to execute code in the context of
	the browser-based client application and maliciously use a token indirectly	the browser-based client application and maliciously use a token indirectly
	through the client. That execution context has access to utilize the signing	through the client. That execution context has access to utilize the signing

	key and thus can produce DPoP proofs to use in conjunction with the token.	key; thus, it can produce DPoP proofs to use in conjunction with the token.
	At this application layer there is most likely no feasible defense against	At this application layer, there is most likely no feasible defense against
	this threat except generally preventing XSS, therefore it is considered	this threat except generally preventing XSS; therefore, it is considered
	out of scope for DPoP.</t>	out of scope for DPoP.</t>
	<t>Malicious XSS code executed in the context of the browser-based client	<t>Malicious XSS code executed in the context of the browser-based client
	application is also in a position to create DPoP proofs with timestamp values in	application is also in a position to create DPoP proofs with timestamp values in
	the future and exfiltrate them in conjunction with a token. These stolen	the future and exfiltrate them in conjunction with a token. These stolen
	artifacts can later be used independent of the client application to	artifacts can later be used independent of the client application to
	access protected resources. To prevent this, servers can optionally require	access protected resources. To prevent this, servers can optionally require
	clients to include a server-chosen value into the proof that cannot be predicted	clients to include a server-chosen value into the proof that cannot be predicted
	by an attacker (nonce). In the absence of the optional nonce, the impact of	by an attacker (nonce). In the absence of the optional nonce, the impact of
	pre-computed DPoP proofs is limited somewhat by the proof being bound to an	pre-computed DPoP proofs is limited somewhat by the proof being bound to an
	access token on protected resource access. Because a proof covering an access	access token on protected resource access. Because a proof covering an access
	token that does not yet exist cannot feasibly be created, access tokens obtained	token that does not yet exist cannot feasibly be created, access tokens obtained
	with an exfiltrated refresh token and pre-computed proofs will be unusable.</t>	with an exfiltrated refresh token and pre-computed proofs will be unusable.</t>
	<t>Additional security considerations are discussed in <xref target="Security">< /xref>.</t>	<t>Additional security considerations are discussed in <xref target="Security">< /xref>.</t>
	</section>	</section>

	<section anchor="concept"><name>Concept</name>	<section anchor="concept"><name>Concept</name>
	<t>The main data structure introduced by this specification is a DPoP	<t>The main data structure introduced by this specification is a DPoP

	proof JWT, described in detail below, which is sent as a header in an	proof JWT that is sent as a header in an
	HTTP request. A client uses a DPoP proof JWT to prove	HTTP request, as described in detail below. A client uses a DPoP proof JWT to pr
		ove
	the possession of a private key corresponding to a certain public key.</t>	the possession of a private key corresponding to a certain public key.</t>

	<t>Roughly speaking, a DPoP proof is a signature over some	<t>Roughly speaking, a DPoP proof is a signature over:</t>
	data of the HTTP request to which it is attached, a timestamp, a unique identifi	<ul>
	er, an optional server-provided nonce,	<li>some data of the
	and a hash of the associated access token when an access token is present within	HTTP request to which it is attached,</li>
	the request.</t>	<li>a timestamp,</li>
		<li>a unique
		identifier,</li>
		<li>an optional server-provided nonce, and</li>
		<li>a hash of the
		associated access token when an access token is present within the
		request.</li>
		</ul>
	<figure anchor="basic-flow"><name>Basic DPoP Flow </name>	<figure anchor="basic-flow"><name>Basic DPoP Flow </name>

	<sourcecode type="ascii-art">+--------+	<artwork type="ascii-art"><![CDATA[
	+---------------+	+--------+ +---------------+
	\| \|--(A)-- Token Request ------------------->\| \|	\| \|--(A)-- Token Request ------------------->\| \|
	\| Client \| (DPoP Proof) \| Authorization \|	\| Client \| (DPoP Proof) \| Authorization \|
	\| \| \| Server \|	\| \| \| Server \|

	\| \|<-(B)-- DPoP-bound Access Token ----------\| \|	\| \|<-(B)-- DPoP-Bound Access Token ----------\| \|
	\| \| (token_type=DPoP) +---------------+	\| \| (token_type=DPoP) +---------------+
	\| \|	\| \|
	\| \|	\| \|
	\| \| +---------------+	\| \| +---------------+

	\| \|--(C)-- DPoP-bound Access Token --------->\| \|	\| \|--(C)-- DPoP-Bound Access Token --------->\| \|
	\| \| (DPoP Proof) \| Resource \|	\| \| (DPoP Proof) \| Resource \|
	\| \| \| Server \|	\| \| \| Server \|

	\| \|<-(D)-- Protected Resource ---------------\| \|	\| \|<-(D)-- Protected Resource ---------------\| \|
	\| \| +---------------+	\| \| +---------------+
	+--------+	+--------+

	</sourcecode>	]]></artwork>
	</figure>	</figure>

	<t>The basic steps of an OAuth flow with DPoP (without the optional nonce) are s hown in <xref target="basic-flow"></xref>:</t>	<t>The basic steps of an OAuth flow with DPoP (without the optional nonce) are s hown in <xref target="basic-flow"></xref>.</t>


	<ul spacing="compact">	<ol type="A" spacing="normal">
	<li>(A) In the Token Request, the client sends an authorization grant	<li>In the token request, the client sends an authorization grant
	(e.g., an authorization code, refresh token, etc.)<br />	(e.g., an authorization code, refresh token, etc.)
	to the authorization server in order to obtain an access token	to the authorization server in order to obtain an access token
	(and potentially a refresh token). The client attaches a DPoP	(and potentially a refresh token). The client attaches a DPoP
	proof to the request in an HTTP header.</li>	proof to the request in an HTTP header.</li>

	<li>(B) The authorization server binds (sender-constrains) the access token to t he	<li>The authorization server binds (sender-constrains) the access token to the
	public key claimed by the client in the DPoP proof; that is, the access token ca nnot	public key claimed by the client in the DPoP proof; that is, the access token ca nnot
	be used without proving possession of the respective private key.	be used without proving possession of the respective private key.

	If a refresh token is issued to a public client, it too is	If a refresh token is issued to a public client, it is also bound to the public
	bound to the public key of the DPoP proof.</li>	key of the DPoP proof.</li>
	<li>(C) To use the access token, the client has to prove	<li>To use the access token, the client has to prove
	possession of the private key by, again, adding a header to the	possession of the private key by, again, adding a header to the
	request that carries a DPoP proof for that request. The resource server needs to	request that carries a DPoP proof for that request. The resource server needs to
	receive information about the public key to which the access token is bound. Thi s	receive information about the public key to which the access token is bound. Thi s
	information may be encoded directly into the access token (for	information may be encoded directly into the access token (for

	JWT structured access tokens) or provided via token	JWT-structured access tokens) or provided via token
	introspection endpoint (not shown).	introspection endpoint (not shown).
	The resource server verifies that the public key to which the	The resource server verifies that the public key to which the
	access token is bound matches the public key of the DPoP proof.	access token is bound matches the public key of the DPoP proof.
	It also verifies that the access token hash in the DPoP proof matches the	It also verifies that the access token hash in the DPoP proof matches the
	access token presented in the request.</li>	access token presented in the request.</li>

	<li>(D) The resource server refuses to serve the request if the	<li>The resource server refuses to serve the request if the
	signature check fails or the data in the DPoP proof is wrong,	signature check fails or if the data in the DPoP proof is wrong,
	e.g., the target URI does not match the URI claim in the DPoP	e.g., the target URI does not match the URI claim in the DPoP
	proof JWT. The access token itself, of course, must also be	proof JWT. The access token itself, of course, must also be
	valid in all other respects.</li>	valid in all other respects.</li>

	</ul>	</ol>
	<t>The DPoP mechanism presented herein is not a client authentication method.	<t>The DPoP mechanism presented herein is not a client authentication method.

	In fact, a primary use case of DPoP is for public clients (e.g., single page	In fact, a primary use case of DPoP is for public clients (e.g., single-page
	applications and applications on a user's device) that do not use client authent ication. Nonetheless, DPoP	applications and applications on a user's device) that do not use client authent ication. Nonetheless, DPoP

	is designed such that it is compatible with <tt>private_key_jwt</tt> and all	is designed to be compatible with <tt>private_key_jwt</tt> and all
	other client authentication methods.</t>	other client authentication methods.</t>

	<t>DPoP does not directly ensure message integrity but relies on the TLS	<t>DPoP does not directly ensure message integrity, but it relies on the TLS
	layer for that purpose. See <xref target="Security"></xref> for details.</t>	layer for that purpose. See <xref target="Security"></xref> for details.</t>
	</section>	</section>

	<section anchor="the-proof"><name>DPoP Proof JWTs</name>	<section anchor="the-proof"><name>DPoP Proof JWTs</name>
	<t>DPoP introduces the concept of a DPoP proof, which is a JWT created by	<t>DPoP introduces the concept of a DPoP proof, which is a JWT created by
	the client and sent with an HTTP request using the <tt>DPoP</tt> header field.	the client and sent with an HTTP request using the <tt>DPoP</tt> header field.
	Each HTTP request requires a unique DPoP proof.</t>	Each HTTP request requires a unique DPoP proof.</t>
	<t>A valid DPoP proof demonstrates to the server that the client holds the priva te	<t>A valid DPoP proof demonstrates to the server that the client holds the priva te
	key that was used to sign the DPoP proof JWT. This enables authorization servers to bind	key that was used to sign the DPoP proof JWT. This enables authorization servers to bind
	issued tokens to the corresponding public key (as described in <xref target="acc ess-token-request"></xref>)	issued tokens to the corresponding public key (as described in <xref target="acc ess-token-request"></xref>)

	and for resource servers to verify the key-binding of tokens that	and enables resource servers to verify the key-binding of tokens that
	it receives (see <xref target="http-auth-scheme"></xref>), which prevents said t okens from	it receives (see <xref target="http-auth-scheme"></xref>), which prevents said t okens from
	being used by any entity that does not have access to the private key.</t>	being used by any entity that does not have access to the private key.</t>
	<t>The DPoP proof demonstrates possession of a key and, by itself, is not	<t>The DPoP proof demonstrates possession of a key and, by itself, is not
	an authentication or access control mechanism. When presented	an authentication or access control mechanism. When presented
	in conjunction with a key-bound access token as described in <xref target="http- auth-scheme"></xref>,	in conjunction with a key-bound access token as described in <xref target="http- auth-scheme"></xref>,
	the DPoP proof provides additional assurance about the legitimacy of the client	the DPoP proof provides additional assurance about the legitimacy of the client
	to present the access token. However, a valid DPoP proof JWT is not sufficient a lone	to present the access token. However, a valid DPoP proof JWT is not sufficient a lone
	to make access control decisions.</t>	to make access control decisions.</t>

	<section anchor="the-dpop-http-header"><name>The DPoP HTTP Header</name>	<section anchor="the-dpop-http-header"><name>The DPoP HTTP Header</name>
	<t>A DPoP proof is included in an HTTP request using the following request heade r field.</t>	<t>A DPoP proof is included in an HTTP request using the following request heade r field.</t>

	<dl spacing="compact">	<dl spacing="compact">

	<dt><tt>DPoP</tt></dt>	<dt><tt>DPoP</tt>:</dt>
	<dd>A JWT that adheres to the structure and syntax of <xref target="DPoP-Proof-S yntax"></xref>.</dd>	<dd>A JWT that adheres to the structure and syntax of <xref target="DPoP-Proof-S yntax"></xref>.</dd>
	</dl>	</dl>

	<t><xref target="dpop-proof-jwt"></xref> shows an example DPoP HTTP header field	<t><xref target="dpop-proof-jwt"></xref> shows an example DPoP HTTP header field
	(with '\' line wrapping per RFC 8792).</t>	. The example uses "\" line wrapping per <xref target="RFC8792"/>.</t>
	<figure anchor="dpop-proof-jwt"><name>Example <tt>DPoP</tt> header </name>	<figure anchor="dpop-proof-jwt"><name>Example <tt>DPoP</tt> Header </name>
	<artwork>DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik\	<sourcecode type="http-message">DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2Ii
		wiandrIjp7Imt0eSI6Ik\
	VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR\	VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR\
	nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE\	nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE\
	QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj\	QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj\
	oiUE9TVCIsImh0dSI6Imh0dHBzOi8vc2VydmVyLmV4YW1wbGUuY29tL3Rva2VuIiwia\	oiUE9TVCIsImh0dSI6Imh0dHBzOi8vc2VydmVyLmV4YW1wbGUuY29tL3Rva2VuIiwia\
	WF0IjoxNTYyMjYyNjE2fQ.2-GxA6T8lP4vfrg8v-FdWP0A0zdrj8igiMLvqRMUvwnQg\	WF0IjoxNTYyMjYyNjE2fQ.2-GxA6T8lP4vfrg8v-FdWP0A0zdrj8igiMLvqRMUvwnQg\
	4PtFLbdLXiOSsX0x7NVY-FNyJK70nfbV37xRZT3Lg	4PtFLbdLXiOSsX0x7NVY-FNyJK70nfbV37xRZT3Lg

	</artwork>	</sourcecode>
	</figure>	</figure>

	<t>Note that per <xref target="RFC9110"></xref> header field names are case-inse	<t>Note that per <xref target="RFC9110"></xref>, header field names are case ins
	nsitive;	ensitive; thus, <tt>DPoP</tt>, <tt>DPOP</tt>, <tt>dpop</tt>, etc., are all valid
	so <tt>DPoP</tt>, <tt>DPOP</tt>, <tt>dpop</tt>, etc., are all valid and equivale	and equivalent header
	nt header	field names. However, case is significant in the header field value.</t>
	field names. Case is significant in the header field value, however.</t>
	<t>The <tt>DPoP</tt> HTTP header field value	<t>The <tt>DPoP</tt> HTTP header field value

	uses the <tt>token68</tt> syntax defined in Section 11.2 of <xref target="RFC911	uses the token68 syntax defined in <xref target="RFC9110" sectionFormat="of" sec
	0"></xref>	tion="11.2"></xref> and is repeated below in <xref target="dpop-header-abnf"></x
	(repeated below in <xref target="dpop-header-abnf"></xref> for ease of reference	ref> for ease of reference.</t>
	).</t>
	<figure anchor="dpop-header-abnf"><name>DPoP header field ABNF </name>	<figure anchor="dpop-header-abnf"><name>DPoP Header Field ABNF</name>
	<artwork> DPoP = token68	<sourcecode type="abnf"><![CDATA[
	token68 = 1*( ALPHA / DIGIT /	DPoP = token68
	"-" / "." / "_" / "~"	token68 = 1*( ALPHA / DIGIT /
	/ "+" / "/" ) *"="	"-" / "." / "_" / "~" / "+" / "/" ) *"="
	</artwork>	]]></sourcecode></figure>
	</figure>
	</section>	</section>

	<section anchor="DPoP-Proof-Syntax"><name>DPoP Proof JWT Syntax</name>	<section anchor="DPoP-Proof-Syntax"><name>DPoP Proof JWT Syntax</name>

	<t>A DPoP proof is a JWT (<xref target="RFC7519"></xref>) that is signed (using	<t>A DPoP proof is a JWT <xref target="RFC7519"></xref> that is signed (using JS
	JSON Web Signature (JWS)	ON Web Signature (JWS) <xref target="RFC7515"></xref>) with a private key chosen
	<xref target="RFC7515"></xref>) with a private key chosen by the client (see bel	by the client (see below). The
	ow). The	JOSE Header of a DPoP JWT <bcp14>MUST</bcp14> contain at least the following par
	JOSE header of a DPoP JWT MUST contain at least the following parameters:</t>	ameters:</t>
		<dl spacing="normal">
	<ul spacing="compact">	<dt><tt>typ</tt>:</dt><dd>A field with the value <tt>dpop+jwt</tt>, which explic
	<li><tt>typ</tt>: with value <tt>dpop+jwt</tt>, which explicitly types the DPoP	itly types the DPoP proof JWT as recommended in <xref target="RFC8725" sectionFo
	proof JWT as recommended in <xref target="RFC8725" sectionFormat="of" relative="	rmat="of" section="3.11"></xref>.</dd>
	#" section="3.11"></xref>.</li>	<dt><tt>alg</tt>:</dt><dd>An identifier for a JWS asymmetric digital signature a
	<li><tt>alg</tt>: an identifier for a JWS asymmetric digital signature algorithm	lgorithm from <xref target="IANA.JOSE.ALGS"></xref>. It
	from <xref target="IANA.JOSE.ALGS"></xref>.	<bcp14>MUST NOT</bcp14> be <tt>none</tt> or an identifier for a symmetric algori
	MUST NOT be <tt>none</tt> or an identifier for a symmetric algorithm (MAC).</li>	thm (Message Authentication Code (MAC)).</dd>
	<li><tt>jwk</tt>: representing the public key chosen by the client, in JSON Web	<dt><tt>jwk</tt>:</dt><dd>Represents the public key chosen by the client in JSON
	Key (JWK) <xref target="RFC7517"></xref>	Web Key (JWK) <xref target="RFC7517"/> format as defined in <xref target="RFC75
	format, as defined in Section 4.1.3 of <xref target="RFC7515"></xref>.	15" sectionFormat="of" section="4.1.3"></xref>. It
	MUST NOT contain a private key.</li>	<bcp14>MUST NOT</bcp14> contain a private key.</dd>
	</ul>	</dl>
	<t>The payload of a DPoP proof MUST contain at least the following claims:</t>	<t>The payload of a DPoP proof <bcp14>MUST</bcp14> contain at least the followin
		g claims:</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li><tt>jti</tt>: Unique identifier for the DPoP proof JWT.	<dt><tt>jti</tt>:</dt><dd>Unique identifier for the DPoP proof JWT.
	The value MUST be assigned such that there is a negligible	The value <bcp14>MUST</bcp14> be assigned such that there is a negligible
	probability that the same value will be assigned to any	probability that the same value will be assigned to any
	other DPoP proof used in the same context during the time window of validity.	other DPoP proof used in the same context during the time window of validity.
	Such uniqueness can be accomplished by encoding (base64url or any other	Such uniqueness can be accomplished by encoding (base64url or any other
	suitable encoding) at least 96 bits of	suitable encoding) at least 96 bits of

	pseudorandom data or by using a version 4 UUID string according to <xref target= "RFC4122"></xref>.	pseudorandom data or by using a version 4 Universally Unique Identifier (UUID) s tring according to <xref target="RFC4122"></xref>.
	The <tt>jti</tt> can be used by the server for replay	The <tt>jti</tt> can be used by the server for replay

	detection and prevention, see <xref target="Token_Replay"></xref>.</li>	detection and prevention; see <xref target="Token_Replay"></xref>.</dd>
	<li><tt>htm</tt>: The value of the HTTP method (Section 9.1 of <xref target="RFC	<dt><tt>htm</tt>:</dt><dd>The value of the HTTP method (<xref target="RFC9110" s
	9110"></xref>) of the	ectionFormat="of" section="9.1"></xref>) of the
	request to which the JWT is attached.</li>	request to which the JWT is attached.</dd>
	<li><tt>htu</tt>: The HTTP target URI (<xref target="RFC9110" sectionFormat="of"	<dt><tt>htu</tt>:</dt><dd>The HTTP target URI (<xref target="RFC9110" sectionFor
	relative="#" section="7.1"></xref>), without query and fragment	mat="of" section="7.1"></xref>) of the request to which the JWT is attached, wit
	parts, of the request to which the JWT is attached.</li>	hout query and fragment
	<li><tt>iat</tt>: Creation timestamp of the JWT (<xref target="RFC7519"></xref>,	parts.</dd>
	section 4.1.6]).</li>	<dt><tt>iat</tt>:</dt><dd>Creation timestamp of the JWT (<xref target="RFC7519"
	</ul>	sectionFormat="of" section="4.1.6"></xref>).</dd>
	<t>When the DPoP proof is used in conjunction with the presentation of an access	</dl>
	token in protected resource access, see	<t>When the DPoP proof is used in conjunction with the presentation of an access
	<xref target="protected-resource-access"></xref>, the DPoP proof MUST also conta	token in protected resource access (see
	in the following claim:</t>	<xref target="protected-resource-access"></xref>), the DPoP proof <bcp14>MUST</b
		cp14> also contain the following claim:</t>
	<ul spacing="compact">	<dl spacing="normal">
	<li><tt>ath</tt>: hash of the access token.	<dt><tt>ath</tt>:</dt><dd>Hash of the access token.
	The value MUST be the result of a base64url encoding (as defined in <xref target	The value <bcp14>MUST</bcp14> be the result of a base64url encoding (as defined
	="RFC7515" sectionFormat="of" relative="#" section="2"></xref>) the SHA-256 <xre	in <xref target="RFC7515" sectionFormat="of" section="2"></xref>) the SHA-256 <x
	f target="SHS"></xref>	ref target="SHS"></xref>
	hash of the ASCII encoding of the associated access token's value.</li>	hash of the ASCII encoding of the associated access token's value.</dd>
	</ul>	</dl>
	<t>When the authentication server or resource server provides a <tt>DPoP-Nonce</ tt> HTTP header	<t>When the authentication server or resource server provides a <tt>DPoP-Nonce</ tt> HTTP header

	in a response (see <xref target="ASNonce"></xref>, <xref target="RSNonce"></xref >), the DPoP proof MUST also contain	in a response (see Sections <xref target="ASNonce" format="counter"></xref> and <xref target="RSNonce" format="counter"></xref>), the DPoP proof <bcp14>MUST</bc p14> also contain
	the following claim:</t>	the following claim:</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li><tt>nonce</tt>: A recent nonce provided via the <tt>DPoP-Nonce</tt> HTTP he	<dt><tt>nonce</tt>:</dt><dd>A recent nonce provided via the <tt>DPoP-Nonce</tt>
	ader.</li>	HTTP header.</dd>
	</ul>	</dl>
	<t>A DPoP proof MAY contain other JOSE header parameters or claims as defined by	<t>A DPoP proof <bcp14>MAY</bcp14> contain other JOSE Header Parameters or claim
	extension,	s as defined by extension,
	profile, or deployment specific requirements.</t>	profile, or deployment-specific requirements.</t>
	<t><xref target="dpop-proof"></xref> is a conceptual example showing the decoded content of the DPoP	<t><xref target="dpop-proof"></xref> is a conceptual example showing the decoded content of the DPoP
	proof in <xref target="dpop-proof-jwt"></xref>. The JSON of the JWT header and p ayload are shown,	proof in <xref target="dpop-proof-jwt"></xref>. The JSON of the JWT header and p ayload are shown,
	but the signature part is omitted. As usual, line breaks and extra spaces	but the signature part is omitted. As usual, line breaks and extra spaces
	are included for formatting and readability.</t>	are included for formatting and readability.</t>

	<figure anchor="dpop-proof"><name>Example JWT content of a <tt>DPoP</tt> proof <	<figure anchor="dpop-proof"><name>Example JWT Content of a <tt>DPoP</tt> Proof</
	/name>	name>
	<artwork>{	<sourcecode>{
	"typ":"dpop+jwt",	"typ":"dpop+jwt",
	"alg":"ES256",	"alg":"ES256",
	"jwk": {	"jwk": {
	"kty":"EC",	"kty":"EC",
	"x":"l8tFrhx-34tV3hRICRDY9zCkDlpBhF42UQUfWVAWBFs",	"x":"l8tFrhx-34tV3hRICRDY9zCkDlpBhF42UQUfWVAWBFs",
	"y":"9VE4jf_Ok_o64zbTTlcuNJajHmt6v9TDVrU0CdvGRDA",	"y":"9VE4jf_Ok_o64zbTTlcuNJajHmt6v9TDVrU0CdvGRDA",
	"crv":"P-256"	"crv":"P-256"
	}	}
	}	}
	.	.
	{	{

	"jti":"-BwC3ESc6acc2lTc",	"jti":"-BwC3ESc6acc2lTc",
	"htm":"POST",	"htm":"POST",
	"htu":"https://server.example.com/token",	"htu":"https://server.example.com/token",
	"iat":1562262616	"iat":1562262616
	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>
	<t>Of the HTTP request, only the HTTP method and URI are	<t>Of the HTTP request, only the HTTP method and URI are

	included in the DPoP JWT, and therefore only these two message parts	included in the DPoP JWT; therefore, only these two message parts
	are covered by the DPoP proof.	are covered by the DPoP proof.

	The idea is sign just enough of the HTTP data to	The idea is to sign just enough of the HTTP data to
	provide reasonable proof-of-possession with respect to the HTTP request.	provide reasonable proof of possession with respect to the HTTP request.
	This design approach of using only a minimal subset of the HTTP header	This design approach of using only a minimal subset of the HTTP header
	data is to avoid the substantial difficulties inherent in attempting to	data is to avoid the substantial difficulties inherent in attempting to
	normalize HTTP messages.	normalize HTTP messages.
	Nonetheless, DPoP proofs can be extended to contain other information of the	Nonetheless, DPoP proofs can be extended to contain other information of the
	HTTP request (see also <xref target="request_integrity"></xref>).</t>	HTTP request (see also <xref target="request_integrity"></xref>).</t>
	</section>	</section>

	<section anchor="checking"><name>Checking DPoP Proofs</name>	<section anchor="checking"><name>Checking DPoP Proofs</name>

	<t>To validate a DPoP proof, the receiving server MUST ensure that</t>	<t>To validate a DPoP proof, the receiving server <bcp14>MUST</bcp14> ensure the following:</t>

	<ol spacing="compact">	<ol spacing="compact">

	<li>there is not more than one <tt>DPoP</tt> HTTP request header field,</li>	<li>There is not more than one <tt>DPoP</tt> HTTP request header field.</li>
	<li>the DPoP HTTP request header field value is a single well-formed JWT,</li>	<li>The DPoP HTTP request header field value is a single and well-formed JWT.</l
	<li>all required claims per <xref target="DPoP-Proof-Syntax"></xref> are contain	i>
	ed in the JWT,</li>	<li>All required claims per <xref target="DPoP-Proof-Syntax"></xref> are contain
	<li>the <tt>typ</tt> JOSE header parameter has the value <tt>dpop+jwt</tt>,</li>	ed in the JWT.</li>
	<li>the <tt>alg</tt> JOSE header parameter indicates a registered asymmetric dig	<li>The <tt>typ</tt> JOSE Header Parameter has the value <tt>dpop+jwt</tt>.</li>
	ital	<li>The <tt>alg</tt> JOSE Header Parameter indicates a registered asymmetric dig
		ital
	signature algorithm <xref target="IANA.JOSE.ALGS"></xref>, is not <tt>none</tt>, is supported by the	signature algorithm <xref target="IANA.JOSE.ALGS"></xref>, is not <tt>none</tt>, is supported by the

	application, and is acceptable per local policy,</li>	application, and is acceptable per local policy.</li>
	<li>the JWT signature verifies with the public key contained in the <tt>jwk</tt>	<li>The JWT signature verifies with the public key contained in the <tt>jwk</tt>
	JOSE header parameter,</li>	JOSE Header Parameter.</li>
	<li>the <tt>jwk</tt> JOSE header parameter does not contain a private key,</li>	<li>The <tt>jwk</tt> JOSE Header Parameter does not contain a private key.</li>
	<li>the <tt>htm</tt> claim matches the HTTP method of the current request,</li>	<li>The <tt>htm</tt> claim matches the HTTP method of the current request.</li>
	<li>the <tt>htu</tt> claim matches the HTTP URI value for the HTTP	<li>The <tt>htu</tt> claim matches the HTTP URI value for the HTTP
	request in which the JWT was received, ignoring any query and	request in which the JWT was received, ignoring any query and

	fragment parts,</li>	fragment parts.</li>
	<li>if the server provided a nonce value to the client,	<li>If the server provided a nonce value to the client,
	the <tt>nonce</tt> claim matches the server-provided nonce value,</li>	the <tt>nonce</tt> claim matches the server-provided nonce value.</li>
	<li>the creation time of the JWT, as determined by either the <tt>iat</tt> claim	<li>The creation time of the JWT, as determined by either the <tt>iat</tt> claim
	or a server managed timestamp via the <tt>nonce</tt> claim, is within an accept	or a server managed timestamp via the <tt>nonce</tt> claim, is within an accept
	able window (see <xref target="Token_Replay"></xref>),</li>	able window (see <xref target="Token_Replay"></xref>).</li>
	<li><t>if presented to a protected resource in conjunction with an access token,	<li><t>If presented to a protected resource in conjunction with an access token,
	</t>	</t>

	<ul spacing="compact">	<ul spacing="compact">

	<li>ensure that the value of the <tt>ath</tt> claim equals the hash of that acce ss token,</li>	<li>ensure that the value of the <tt>ath</tt> claim equals the hash of that acce ss token, and</li>
	<li>confirm that the public key to which the access token is bound matches the p ublic key from the DPoP proof.</li>	<li>confirm that the public key to which the access token is bound matches the p ublic key from the DPoP proof.</li>
	</ul></li>	</ul></li>
	</ol>	</ol>
	<t>To reduce the likelihood of false negatives,	<t>To reduce the likelihood of false negatives,

	servers SHOULD employ Syntax-Based Normalization (<xref target="RFC3986" section	servers <bcp14>SHOULD</bcp14> employ syntax-based normalization (<xref target="R
	Format="of" relative="#" section="6.2.2"></xref>) and Scheme-Based	FC3986" sectionFormat="of" section="6.2.2"></xref>) and scheme-based
	Normalization (<xref target="RFC3986" sectionFormat="of" relative="#" section="6	normalization (<xref target="RFC3986" sectionFormat="of" section="6.2.3"></xref>
	.2.3"></xref>) before comparing the <tt>htu</tt> claim.</t>	) before comparing the <tt>htu</tt> claim.</t>
	<t>These checks may be performed in any order.</t>	<t>These checks may be performed in any order.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="access-token-request"><name>DPoP Access Token Request</name>	<section anchor="access-token-request"><name>DPoP Access Token Request</name>

	<t>To request an access token that is bound to a public key using DPoP, the clie nt MUST	<t>To request an access token that is bound to a public key using DPoP, the clie nt <bcp14>MUST</bcp14>
	provide a valid DPoP proof JWT in a <tt>DPoP</tt> header when making an access t oken	provide a valid DPoP proof JWT in a <tt>DPoP</tt> header when making an access t oken
	request to the authorization server's token endpoint. This is applicable for all	request to the authorization server's token endpoint. This is applicable for all

	access token requests regardless of grant type (including, for example,	access token requests regardless of grant type (e.g.,
	the common <tt>authorization_code</tt> and <tt>refresh_token</tt> grant types bu	the common <tt>authorization_code</tt> and <tt>refresh_token</tt> grant types an
	t also extension grants	d extension grants
	such as the JWT authorization grant <xref target="RFC7523"></xref>). The HTTP re quest shown in	such as the JWT authorization grant <xref target="RFC7523"></xref>). The HTTP re quest shown in
	<xref target="token-request-code"></xref> illustrates such an access	<xref target="token-request-code"></xref> illustrates such an access
	token request using an authorization code grant with a DPoP proof JWT	token request using an authorization code grant with a DPoP proof JWT

	in the <tt>DPoP</tt> header	in the <tt>DPoP</tt> header. <xref target="token-request-code"/> uses "\" line w
	(with '\' line wrapping per RFC 8792).</t>	rapping per <xref target="RFC8792"/>.</t>
	<figure anchor="token-request-code"><name>Token Request for a DPoP sender-constr	<figure anchor="token-request-code"><name>Token Request for a DPoP Sender-Constr
	ained token using an authorization code </name>	ained Token Using an Authorization Code</name>
	<artwork>POST /token HTTP/1.1	<sourcecode type="http-message"><![CDATA[POST /token HTTP/1.1
	Host: server.example.com	Host: server.example.com
	Content-Type: application/x-www-form-urlencoded	Content-Type: application/x-www-form-urlencoded
	DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik\	DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik\
	VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR\	VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR\
	nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE\	nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE\
	QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj\	QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj\
	oiUE9TVCIsImh0dSI6Imh0dHBzOi8vc2VydmVyLmV4YW1wbGUuY29tL3Rva2VuIiwia\	oiUE9TVCIsImh0dSI6Imh0dHBzOi8vc2VydmVyLmV4YW1wbGUuY29tL3Rva2VuIiwia\
	WF0IjoxNTYyMjYyNjE2fQ.2-GxA6T8lP4vfrg8v-FdWP0A0zdrj8igiMLvqRMUvwnQg\	WF0IjoxNTYyMjYyNjE2fQ.2-GxA6T8lP4vfrg8v-FdWP0A0zdrj8igiMLvqRMUvwnQg\
	4PtFLbdLXiOSsX0x7NVY-FNyJK70nfbV37xRZT3Lg	4PtFLbdLXiOSsX0x7NVY-FNyJK70nfbV37xRZT3Lg

	grant_type=authorization_code\	grant_type=authorization_code\

	&client_id=s6BhdRkqt\	&client_id=s6BhdRkqt\
	&code=SplxlOBeZQQYbYS6WxSbIA	&code=SplxlOBeZQQYbYS6WxSbIA
	&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb\	&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb\
	&code_verifier=bEaL42izcC-o-xBk0K2vuJ6U-y1p9r_wW2dFWIWgjz-	&code_verifier=bEaL42izcC-o-xBk0K2vuJ6U-y1p9r_wW2dFWIWgjz-
	</artwork>	]]></sourcecode>
	</figure>	</figure>

	<t>The <tt>DPoP</tt> HTTP header field MUST contain a valid DPoP proof JWT.	<t>The <tt>DPoP</tt> HTTP header field <bcp14>MUST</bcp14> contain a valid DPoP proof JWT.
	If the DPoP proof is invalid, the authorization server issues an error	If the DPoP proof is invalid, the authorization server issues an error

	response per Section 5.2 of <xref target="RFC6749"></xref> with <tt>invalid_dpop _proof</tt> as the	response per <xref target="RFC6749" sectionFormat="of" section="5.2"></xref> wit h <tt>invalid_dpop_proof</tt> as the
	value of the <tt>error</tt> parameter.</t>	value of the <tt>error</tt> parameter.</t>

	<t>To sender-constrain the access token, after checking the validity of the	<t>To sender-constrain the access token after checking the validity of the
	DPoP proof, the authorization server associates the issued access token with the	DPoP proof, the authorization server associates the issued access token with the
	public key from the DPoP proof, which can be accomplished as described in <xref target="Confirmation"></xref>.	public key from the DPoP proof, which can be accomplished as described in <xref target="Confirmation"></xref>.

	A <tt>token_type</tt> of <tt>DPoP</tt> MUST be included in the access token	A <tt>token_type</tt> of <tt>DPoP</tt> <bcp14>MUST</bcp14> be included in the ac cess token
	response to signal to the client that the access token was bound to	response to signal to the client that the access token was bound to
	its DPoP key and can be used as described in <xref target="http-auth-scheme"></x ref>.	its DPoP key and can be used as described in <xref target="http-auth-scheme"></x ref>.
	The example response shown in <xref target="token-response"></xref> illustrates such a	The example response shown in <xref target="token-response"></xref> illustrates such a
	response.</t>	response.</t>
	<figure anchor="token-response"><name>Access Token Response </name>	<figure anchor="token-response"><name>Access Token Response </name>

	<artwork>HTTP/1.1 200 OK	<sourcecode type="http-message">HTTP/1.1 200 OK
	Content-Type: application/json	Content-Type: application/json
	Cache-Control: no-store	Cache-Control: no-store

	{	{

	"access_token": "Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU&quo	"access_token": "Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU",
	t;,	"token_type": "DPoP",
	"token_type": "DPoP",	"expires_in": 2677,
	"expires_in": 2677,	"refresh_token": "Q..Zkm29lexi8VnWg2zPW1x-tgGad0Ibc3s3EwM_Ni4-g"
	"refresh_token": "Q..Zkm29lexi8VnWg2zPW1x-tgGad0Ibc3s3EwM_Ni4-g&
	quot;
	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>

	<t>The example response in <xref target="token-response"></xref> includes a refr esh token which the	<t>The example response in <xref target="token-response"></xref> includes a refr esh token that the
	client can use to obtain a new access token when the previous one expires.	client can use to obtain a new access token when the previous one expires.
	Refreshing an access token is a token request using the <tt>refresh_token</tt>	Refreshing an access token is a token request using the <tt>refresh_token</tt>
	grant type made to the authorization server's token endpoint. As with	grant type made to the authorization server's token endpoint. As with
	all access token requests, the client makes it a DPoP request by including	all access token requests, the client makes it a DPoP request by including

	a DPoP proof, as shown in the <xref target="token-request-rt"></xref> example	a DPoP proof, as shown in <xref target="token-request-rt"></xref>. <xref target=
	(with '\' line wrapping per RFC 8792).</t>	"token-request-rt"/> uses "\" line wrapping per <xref target="RFC8792"/>.</t>
	<figure anchor="token-request-rt"><name>Token Request for a DPoP-bound Token usi	<figure anchor="token-request-rt"><name>Token Request for a DPoP-Bound Token Usi
	ng a Refresh Token </name>	ng a Refresh Token </name>
	<artwork>POST /token HTTP/1.1	<sourcecode type="http-message"><![CDATA[POST /token HTTP/1.1
	Host: server.example.com	Host: server.example.com
	Content-Type: application/x-www-form-urlencoded	Content-Type: application/x-www-form-urlencoded
	DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik\	DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik\
	VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR\	VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR\
	nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE\	nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE\
	QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj\	QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj\
	oiUE9TVCIsImh0dSI6Imh0dHBzOi8vc2VydmVyLmV4YW1wbGUuY29tL3Rva2VuIiwia\	oiUE9TVCIsImh0dSI6Imh0dHBzOi8vc2VydmVyLmV4YW1wbGUuY29tL3Rva2VuIiwia\
	WF0IjoxNTYyMjY1Mjk2fQ.pAqut2IRDm_De6PR93SYmGBPXpwrAk90e8cP2hjiaG5Qs\	WF0IjoxNTYyMjY1Mjk2fQ.pAqut2IRDm_De6PR93SYmGBPXpwrAk90e8cP2hjiaG5Qs\
	GSuKDYW7_X620BxqhvYC8ynrrvZLTk41mSRroapUA	GSuKDYW7_X620BxqhvYC8ynrrvZLTk41mSRroapUA

	grant_type=refresh_token\	grant_type=refresh_token\

	&client_id=s6BhdRkqt\	&client_id=s6BhdRkqt\
	&refresh_token=Q..Zkm29lexi8VnWg2zPW1x-tgGad0Ibc3s3EwM_Ni4-g	&refresh_token=Q..Zkm29lexi8VnWg2zPW1x-tgGad0Ibc3s3EwM_Ni4-g
	</artwork>	]]></sourcecode>
	</figure>	</figure>
	<t>When an authorization server supporting DPoP issues a	<t>When an authorization server supporting DPoP issues a
	refresh token to a public client that presents a valid DPoP proof at the	refresh token to a public client that presents a valid DPoP proof at the

	token endpoint, the refresh token MUST be bound	token endpoint, the refresh token <bcp14>MUST</bcp14> be bound
	to the respective public key. The binding MUST be validated when the refresh	to the respective public key. The binding <bcp14>MUST</bcp14> be validated when
		the refresh
	token is later presented to get new access tokens. As a result, such a client	token is later presented to get new access tokens. As a result, such a client

	MUST present a DPoP proof for the same key that was used to obtain the refresh	<bcp14>MUST</bcp14> present a DPoP proof for the same key that was used to obtai n the refresh
	token each time that refresh token is used to obtain a new access token.	token each time that refresh token is used to obtain a new access token.
	The implementation details of the binding of the refresh token are at the discre tion of	The implementation details of the binding of the refresh token are at the discre tion of
	the authorization server. Since the authorization server both produces and	the authorization server. Since the authorization server both produces and
	validates its refresh tokens, there is no interoperability	validates its refresh tokens, there is no interoperability
	consideration in the specific details of the binding.</t>	consideration in the specific details of the binding.</t>

	<t>An authorization server MAY elect to issue access tokens which are not DPoP b ound,	<t>An authorization server <bcp14>MAY</bcp14> elect to issue access tokens that are not DPoP bound,
	which is signaled to the client with a value of <tt>Bearer</tt> in the <tt>token _type</tt> parameter	which is signaled to the client with a value of <tt>Bearer</tt> in the <tt>token _type</tt> parameter
	of the access token response per <xref target="RFC6750"></xref>. For a public cl ient that is	of the access token response per <xref target="RFC6750"></xref>. For a public cl ient that is
	also issued a refresh token, this has the effect of DPoP-binding the refresh tok en	also issued a refresh token, this has the effect of DPoP-binding the refresh tok en
	alone, which can improve the security posture even when protected resources are not	alone, which can improve the security posture even when protected resources are not
	updated to support DPoP.</t>	updated to support DPoP.</t>
	<t>If the access token response contains a different <tt>token_type</tt> value t han <tt>DPoP</tt>, the	<t>If the access token response contains a different <tt>token_type</tt> value t han <tt>DPoP</tt>, the

	access token protection provided by DPoP is not given. The client MUST discard t	access token protection provided by DPoP is not given. The client <bcp14>MUST</b
	he response in this	cp14> discard the response in this
	case, if this protection is deemed important for the security of the	case if this protection is deemed important for the security of the
	application; otherwise, it may continue as in a regular OAuth interaction.</t>	application; otherwise, the client may continue as in a regular OAuth interactio
		n.</t>
	<t>Refresh tokens issued to confidential clients (those having	<t>Refresh tokens issued to confidential clients (those having
	established authentication credentials with the authorization server)	established authentication credentials with the authorization server)
	are not bound to the DPoP proof public key because they are already	are not bound to the DPoP proof public key because they are already
	sender-constrained with a different existing mechanism. The OAuth 2.0 Authorizat ion	sender-constrained with a different existing mechanism. The OAuth 2.0 Authorizat ion
	Framework <xref target="RFC6749"></xref> already requires that an authorization server bind	Framework <xref target="RFC6749"></xref> already requires that an authorization server bind
	refresh tokens to the client to which they were issued and that	refresh tokens to the client to which they were issued and that
	confidential clients authenticate to the authorization server when	confidential clients authenticate to the authorization server when
	presenting a refresh token. As a result, such refresh tokens	presenting a refresh token. As a result, such refresh tokens
	are sender-constrained by way of the client identifier and the associated	are sender-constrained by way of the client identifier and the associated
	authentication requirement. This existing sender-constraining mechanism	authentication requirement. This existing sender-constraining mechanism
	is more flexible (e.g., it allows credential rotation for the client	is more flexible (e.g., it allows credential rotation for the client
	without invalidating refresh tokens) than binding directly to a particular publi c key.</t>	without invalidating refresh tokens) than binding directly to a particular publi c key.</t>

	<section anchor="as-meta"><name>Authorization Server Metadata</name>	<section anchor="as-meta"><name>Authorization Server Metadata</name>
	<t>This document introduces the following authorization server metadata	<t>This document introduces the following authorization server metadata
	<xref target="RFC8414"></xref> parameter to signal support for DPoP in general a nd the specific	<xref target="RFC8414"></xref> parameter to signal support for DPoP in general a nd the specific
	JWS <tt>alg</tt> values the authorization server supports for DPoP proof JWTs.</ t>	JWS <tt>alg</tt> values the authorization server supports for DPoP proof JWTs.</ t>

	<dl spacing="compact">	<dl spacing="compact">

	<dt><tt>dpop_signing_alg_values_supported</tt></dt>	<dt><tt>dpop_signing_alg_values_supported</tt>:</dt>
	<dd>A JSON array containing a list of the JWS <tt>alg</tt> values (from the <xre f target="IANA.JOSE.ALGS"></xref> registry) supported	<dd>A JSON array containing a list of the JWS <tt>alg</tt> values (from the <xre f target="IANA.JOSE.ALGS"></xref> registry) supported
	by the authorization server for DPoP proof JWTs.</dd>	by the authorization server for DPoP proof JWTs.</dd>
	</dl>	</dl>
	</section>	</section>

	<section anchor="client-meta"><name>Client Registration Metadata</name>	<section anchor="client-meta"><name>Client Registration Metadata</name>
	<t>The Dynamic Client Registration Protocol <xref target="RFC7591"></xref> defin es an API	<t>The Dynamic Client Registration Protocol <xref target="RFC7591"></xref> defin es an API
	for dynamically registering OAuth 2.0 client metadata with authorization servers .	for dynamically registering OAuth 2.0 client metadata with authorization servers .
	The metadata defined by <xref target="RFC7591"></xref>, and registered extension s to it,	The metadata defined by <xref target="RFC7591"></xref>, and registered extension s to it,
	also imply a general data model for clients that is useful for authorization ser ver implementations	also imply a general data model for clients that is useful for authorization ser ver implementations
	even when the Dynamic Client Registration Protocol isn't in play.	even when the Dynamic Client Registration Protocol isn't in play.
	Such implementations will typically have some sort of user interface available f or managing client configuration.</t>	Such implementations will typically have some sort of user interface available f or managing client configuration.</t>
	<t>This document introduces the following client registration metadata	<t>This document introduces the following client registration metadata
	<xref target="RFC7591"></xref> parameter to indicate that the client always uses	<xref target="RFC7591"></xref> parameter to indicate that the client always uses
	DPoP when requesting tokens from the authorization server.</t>	DPoP when requesting tokens from the authorization server.</t>

	<dl spacing="compact">	<dl spacing="compact">

	<dt><tt>dpop_bound_access_tokens</tt></dt>	<dt><tt>dpop_bound_access_tokens</tt>:</dt>
	<dd>Boolean value specifying whether the client always uses DPoP for token reque	<dd>A boolean value specifying whether the client always uses DPoP for token req
	sts. If omitted, the default value is <tt>false</tt>.</dd>	uests. If omitted, the default value is <tt>false</tt>.</dd>
	</dl>	</dl>

	<t>If <tt>true</tt>, the authorization server MUST reject token requests from th is client that do not contain the DPoP header.</t>	<t>If the value is <tt>true</tt>, the authorization server <bcp14>MUST</bcp14> r eject token requests from the client that do not contain the DPoP header.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="Confirmation"><name>Public Key Confirmation</name>	<section anchor="Confirmation"><name>Public Key Confirmation</name>

	<t>Resource servers MUST be able to reliably identify whether	<t>Resource servers <bcp14>MUST</bcp14> be able to reliably identify whether
	an access token is DPoP-bound and ascertain sufficient information	an access token is DPoP-bound and ascertain sufficient information
	to verify the binding to the public key of the DPoP proof (see <xref target="htt p-auth-scheme"></xref>).	to verify the binding to the public key of the DPoP proof (see <xref target="htt p-auth-scheme"></xref>).
	Such a binding is accomplished by associating the public key	Such a binding is accomplished by associating the public key
	with the token in a way that can be	with the token in a way that can be
	accessed by the protected resource, such as embedding the JWK	accessed by the protected resource, such as embedding the JWK
	hash in the issued access token directly, using the syntax described	hash in the issued access token directly, using the syntax described
	in <xref target="jwk-thumb-jwt"></xref>, or through token introspection as descr ibed in	in <xref target="jwk-thumb-jwt"></xref>, or through token introspection as descr ibed in

	<xref target="jwk-thumb-intro"></xref>. Other methods of associating a	<xref target="jwk-thumb-intro"></xref>.
	public key with an access token are possible, per agreement by the	Other methods of associating a
	authorization server and the protected resource, but are beyond the	public key with an access token are possible per an agreement by the
		authorization server and the protected resource; however, they are beyond the
	scope of this specification.</t>	scope of this specification.</t>

	<t>Resource servers supporting DPoP MUST ensure that the public key from	<t>Resource servers supporting DPoP <bcp14>MUST</bcp14> ensure that the public k ey from
	the DPoP proof matches the one bound to the access token.</t>	the DPoP proof matches the one bound to the access token.</t>

	<section anchor="jwk-thumb-jwt"><name>JWK Thumbprint Confirmation Method</name>	<section anchor="jwk-thumb-jwt"><name>JWK Thumbprint Confirmation Method</name>
	<t>When access tokens are represented as JWTs <xref target="RFC7519"></xref>,	<t>When access tokens are represented as JWTs <xref target="RFC7519"></xref>,
	the public key information is represented	the public key information is represented
	using the <tt>jkt</tt> confirmation method member defined herein.	using the <tt>jkt</tt> confirmation method member defined herein.
	To convey the hash of a public key in a JWT, this specification	To convey the hash of a public key in a JWT, this specification
	introduces the following JWT Confirmation Method <xref target="RFC7800"></xref> member for	introduces the following JWT Confirmation Method <xref target="RFC7800"></xref> member for
	use under the <tt>cnf</tt> claim.</t>	use under the <tt>cnf</tt> claim.</t>

	<dl spacing="compact">	<dl spacing="compact">

	<dt><tt>jkt</tt></dt>	<dt><tt>jkt</tt>:</dt>
	<dd>JWK SHA-256 Thumbprint Confirmation Method. The value of the <tt>jkt</tt> me	<dd>JWK SHA-256 Thumbprint confirmation method. The value of the <tt>jkt</tt> me
	mber	mber
	MUST be the base64url encoding (as defined in <xref target="RFC7515"></xref>)	<bcp14>MUST</bcp14> be the base64url encoding (as defined in <xref target="RFC75
		15"></xref>)
	of the JWK SHA-256 Thumbprint (according to <xref target="RFC7638"></xref>) of t he DPoP public key	of the JWK SHA-256 Thumbprint (according to <xref target="RFC7638"></xref>) of t he DPoP public key
	(in JWK format) to which the access token is bound.</dd>	(in JWK format) to which the access token is bound.</dd>
	</dl>	</dl>

	<t>The following example JWT in <xref target="cnf-claim-jwt"></xref> with decode d JWT payload shown in	<t>The following example JWT in <xref target="cnf-claim-jwt"></xref> with a deco ded JWT payload shown in
	<xref target="cnf-claim"></xref> contains a <tt>cnf</tt> claim with the <tt>jkt< /tt> JWK Thumbprint confirmation	<xref target="cnf-claim"></xref> contains a <tt>cnf</tt> claim with the <tt>jkt< /tt> JWK Thumbprint confirmation
	method member. The <tt>jkt</tt> value in these examples is the hash of the publ ic key	method member. The <tt>jkt</tt> value in these examples is the hash of the publ ic key

	from the DPoP proofs in the examples in <xref target="access-token-request"></xr	from the DPoP proofs in the examples shown in <xref target="access-token-request
	ef>.	"></xref>.
	(The example uses '\' line wrapping per RFC 8792.)</t>	The example uses "\" line wrapping per <xref target="RFC8792"/>.</t>
	<figure anchor="cnf-claim-jwt"><name>JWT containing a JWK SHA-256 Thumbprint Con	<figure anchor="cnf-claim-jwt"><name>JWT Containing a JWK SHA-256 Thumbprint Con
	firmation </name>	firmation </name>
	<artwork>eyJhbGciOiJFUzI1NiIsImtpZCI6IkJlQUxrYiJ9.eyJzdWIiOiJzb21lb25lQGV4YW1\	<sourcecode type="jwt">eyJhbGciOiJFUzI1NiIsImtpZCI6IkJlQUxrYiJ9.eyJzdWIiOiJzb21l
		b25lQGV4YW1\
	wbGUuY29tIiwiaXNzIjoiaHR0cHM6Ly9zZXJ2ZXIuZXhhbXBsZS5jb20iLCJuYmYiOjE\	wbGUuY29tIiwiaXNzIjoiaHR0cHM6Ly9zZXJ2ZXIuZXhhbXBsZS5jb20iLCJuYmYiOjE\
	1NjIyNjI2MTEsImV4cCI6MTU2MjI2NjIxNiwiY25mIjp7ImprdCI6IjBaY09DT1JaTll\	1NjIyNjI2MTEsImV4cCI6MTU2MjI2NjIxNiwiY25mIjp7ImprdCI6IjBaY09DT1JaTll\
	5LURXcHFxMzBqWnlKR0hUTjBkMkhnbEJWM3VpZ3VBNEkifX0.3Tyo8VTcn6u_PboUmAO\	5LURXcHFxMzBqWnlKR0hUTjBkMkhnbEJWM3VpZ3VBNEkifX0.3Tyo8VTcn6u_PboUmAO\
	YUY1kfAavomW_YwYMkmRNizLJoQzWy2fCo79Zi5yObpIzjWb5xW4OGld7ESZrh0fsrA	YUY1kfAavomW_YwYMkmRNizLJoQzWy2fCo79Zi5yObpIzjWb5xW4OGld7ESZrh0fsrA

	</artwork>	</sourcecode>
	</figure>	</figure>
	<figure anchor="cnf-claim"><name>JWT Claims Set with a JWK SHA-256 Thumbprint Co nfirmation </name>	<figure anchor="cnf-claim"><name>JWT Claims Set with a JWK SHA-256 Thumbprint Co nfirmation </name>

	<artwork>{	<sourcecode type="json">{
	"sub":"someone@example.com",	"sub":"someone@example.com",
	"iss":"https://server.example.com",	"iss":"https://server.example.com",
	"nbf":1562262611,	"nbf":1562262611,
	"exp":1562266216,	"exp":1562266216,
	"cnf":	"cnf":
	{	{

	"jkt":"0ZcOCORZNYy-DWpqq30jZyJGHTN0d2HglBV3uiguA4I"	"jkt":"0ZcOCORZNYy-DWpqq30jZyJGHTN0d2HglBV3uiguA4I"
	}	}
	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>
	</section>	</section>

	<section anchor="jwk-thumb-intro"><name>JWK Thumbprint Confirmation Method in To ken Introspection</name>	<section anchor="jwk-thumb-intro"><name>JWK Thumbprint Confirmation Method in To ken Introspection</name>

	<t>OAuth 2.0 Token Introspection <xref target="RFC7662"></xref> defines a method for a	<t>"OAuth 2.0 Token Introspection" <xref target="RFC7662"></xref> defines a meth od for a
	protected resource to query an authorization server about the active	protected resource to query an authorization server about the active

	state of an access token as well as to determine metainformation	state of an access token. The protected resource also determines metainformation
	about the token.</t>	about the token.</t>
	<t>For a DPoP-bound access token, the hash of the public key to which the token	<t>For a DPoP-bound access token, the hash of the public key to which the token
	is bound is conveyed to the protected resource as metainformation in a token	is bound is conveyed to the protected resource as metainformation in a token
	introspection response. The hash is conveyed using the same <tt>cnf</tt> content with	introspection response. The hash is conveyed using the same <tt>cnf</tt> content with
	<tt>jkt</tt> member structure as the JWK Thumbprint confirmation method, describ ed in	<tt>jkt</tt> member structure as the JWK Thumbprint confirmation method, describ ed in
	<xref target="jwk-thumb-jwt"></xref>, as a top-level member of the	<xref target="jwk-thumb-jwt"></xref>, as a top-level member of the
	introspection response JSON. Note that the resource server	introspection response JSON. Note that the resource server

	does not send a DPoP proof with the introspection request and the authorization	does not send a DPoP proof with the introspection request, and the authorization
	server does not validate an access token's DPoP binding at the introspection	server does not validate an access token's DPoP binding at the introspection

	endpoint. Rather the resource server uses the data of the introspection response	endpoint. Rather, the resource server uses the data of the introspection respons e
	to validate the access token binding itself locally.</t>	to validate the access token binding itself locally.</t>

	<t>If the <tt>token_type</tt> member is included in the introspection response, it MUST contain	<t>If the <tt>token_type</tt> member is included in the introspection response, it <bcp14>MUST</bcp14> contain
	the value <tt>DPoP</tt>.</t>	the value <tt>DPoP</tt>.</t>
	<t>The example introspection request in <xref target="introspect-req"></xref> an d corresponding response in	<t>The example introspection request in <xref target="introspect-req"></xref> an d corresponding response in
	<xref target="introspect-resp"></xref> illustrate an introspection exchange for the example DPoP-bound	<xref target="introspect-resp"></xref> illustrate an introspection exchange for the example DPoP-bound
	access token that was issued in <xref target="token-response"></xref>.</t>	access token that was issued in <xref target="token-response"></xref>.</t>
	<figure anchor="introspect-req"><name>Example Introspection Request </name>	<figure anchor="introspect-req"><name>Example Introspection Request </name>

	<artwork>POST /as/introspect.oauth2 HTTP/1.1	<sourcecode type="http-message">POST /as/introspect.oauth2 HTTP/1.1
	Host: server.example.com	Host: server.example.com
	Content-Type: application/x-www-form-urlencoded	Content-Type: application/x-www-form-urlencoded
	Authorization: Basic cnM6cnM6TWt1LTZnX2xDektJZHo0ZnNON2tZY3lhK1Rp	Authorization: Basic cnM6cnM6TWt1LTZnX2xDektJZHo0ZnNON2tZY3lhK1Rp

	token=Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU	token=Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU

	</artwork>	</sourcecode>
	</figure>	</figure>
	<figure anchor="introspect-resp"><name>Example Introspection Response for a DPoP -Bound Access Token </name>	<figure anchor="introspect-resp"><name>Example Introspection Response for a DPoP -Bound Access Token </name>

	<artwork>HTTP/1.1 200 OK	<sourcecode>HTTP/1.1 200 OK
	Content-Type: application/json	Content-Type: application/json
	Cache-Control: no-store	Cache-Control: no-store

	{	{

	"active": true,	"active": true,
	"sub": "someone@example.com",	"sub": "someone@example.com",
	"iss": "https://server.example.com",	"iss": "https://server.example.com",
	"nbf": 1562262611,	"nbf": 1562262611,
	"exp": 1562266216,	"exp": 1562266216,
	"cnf":	"cnf":
	{	{

	"jkt": "0ZcOCORZNYy-DWpqq30jZyJGHTN0d2HglBV3uiguA4I"	"jkt": "0ZcOCORZNYy-DWpqq30jZyJGHTN0d2HglBV3uiguA4I"
	}	}
	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>
	</section>	</section>
	</section>	</section>

	<section anchor="protected-resource-access"><name>Protected Resource Access</nam e>	<section anchor="protected-resource-access"><name>Protected Resource Access</nam e>

	<t>Requests to DPoP protected resources	<t>Requests to DPoP-protected resources
	MUST include both a DPoP proof as per <xref target="the-proof"></xref> and	<bcp14>MUST</bcp14> include both a DPoP proof as per <xref target="the-proof"></
		xref> and
	the access token as described in <xref target="http-auth-scheme"></xref>.	the access token as described in <xref target="http-auth-scheme"></xref>.

	The DPoP proof MUST include the <tt>ath</tt> claim with a valid hash of the	The DPoP proof <bcp14>MUST</bcp14> include the <tt>ath</tt> claim with a valid h ash of the
	associated access token.</t>	associated access token.</t>
	<t>Binding the token value to the proof in this way prevents a proof	<t>Binding the token value to the proof in this way prevents a proof
	to be used with multiple different access token values across different requests .	to be used with multiple different access token values across different requests .
	For example, if a client holds tokens bound to two different resource owners, AT 1 and AT2,	For example, if a client holds tokens bound to two different resource owners, AT 1 and AT2,

	and uses the same key when talking to the AS, it's possible that these tokens co uld be swapped.	and uses the same key when talking to the authorization server, it's possible th at these tokens could be swapped.
	Without the <tt>ath</tt> field to bind it, a captured signature applied to AT1 c ould be	Without the <tt>ath</tt> field to bind it, a captured signature applied to AT1 c ould be
	replayed with AT2 instead, changing the rights and access of the intended reques t.	replayed with AT2 instead, changing the rights and access of the intended reques t.
	This same substitution prevention remains for rotated access tokens within the s ame	This same substitution prevention remains for rotated access tokens within the s ame
	combination of client and resource owner -- a rotated token value would require the	combination of client and resource owner -- a rotated token value would require the
	calculation of a new proof. This binding additionally ensures that a proof inten ded for use	calculation of a new proof. This binding additionally ensures that a proof inten ded for use
	with the access token is not usable without an access token, or vice-versa.</t>	with the access token is not usable without an access token, or vice-versa.</t>
	<t>The resource server is required to calculate the hash of the token value pres ented	<t>The resource server is required to calculate the hash of the token value pres ented
	and verify that it is the same as the hash value in the <tt>ath</tt> field as de scribed in <xref target="checking"></xref>.	and verify that it is the same as the hash value in the <tt>ath</tt> field as de scribed in <xref target="checking"></xref>.
	Since the <tt>ath</tt> field value is covered by the DPoP proof's signature, its inclusion binds	Since the <tt>ath</tt> field value is covered by the DPoP proof's signature, its inclusion binds
	the access token value to the holder of the key used to generate the signature.< /t>	the access token value to the holder of the key used to generate the signature.< /t>
	<t>Note that the <tt>ath</tt> field alone does not prevent replay of the DPoP pr oof or provide binding	<t>Note that the <tt>ath</tt> field alone does not prevent replay of the DPoP pr oof or provide binding
	to the request in which the proof is presented, and it is still important to che ck the time	to the request in which the proof is presented, and it is still important to che ck the time

	window of the proof as well as the included message parameters such as <tt>htm</ tt> and <tt>htu</tt>.</t>	window of the proof as well as the included message parameters, such as <tt>htm< /tt> and <tt>htu</tt>.</t>

	<section anchor="http-auth-scheme"><name>The DPoP Authentication Scheme</name>	<section anchor="http-auth-scheme"><name>The DPoP Authentication Scheme</name>
	<t>A DPoP-bound access token is sent using the <tt>Authorization</tt> request	<t>A DPoP-bound access token is sent using the <tt>Authorization</tt> request

	header field per Section 11.6.2 of <xref target="RFC9110"></xref> using an	header field per <xref target="RFC9110" sectionFormat="of" section="11.6.2"></xr
	authentication scheme of <tt>DPoP</tt>. The syntax of the <tt>Authorization</tt>	ef> with an authentication scheme of <tt>DPoP</tt>. The syntax of the <tt>Author
		ization</tt>
	header field for the <tt>DPoP</tt> scheme	header field for the <tt>DPoP</tt> scheme

	uses the <tt>token68</tt> syntax defined in Section 11.2 of <xref target="RFC911	uses the token68 syntax defined in <xref target="RFC9110" sectionFormat="of" sec
	0"></xref>	tion="11.2"></xref> for credentials and is repeated below for ease of reference.
	(repeated below for ease of reference) for credentials.
	The ABNF notation syntax for DPoP authentication scheme credentials is as follow s:</t>	The ABNF notation syntax for DPoP authentication scheme credentials is as follow s:</t>

	<figure><name>DPoP Authentication Scheme ABNF	<figure anchor="dpop-auth-scheme-abnf"><name>DPoP Authentication Scheme ABNF
	</name>	</name>

	<artwork> token68 = 1*( ALPHA / DIGIT /	<sourcecode type="abnf"><![CDATA[
	"-" / "." / "_" / "~"	token68 = 1*( ALPHA / DIGIT /
	/ "+" / "/" ) *"="	"-" / "." / "_" / "~" / "+" / "/" ) *"="


	credentials = "DPoP" 1*SP token68	credentials = "DPoP" 1*SP token68
	</artwork>	]]></sourcecode>
	</figure>	</figure>

	<t>For such an access token, a resource server MUST check that a DPoP proof	<t>For such an access token, a resource server <bcp14>MUST</bcp14> check that a DPoP proof
	was also received in the <tt>DPoP</tt> header field of the HTTP request,	was also received in the <tt>DPoP</tt> header field of the HTTP request,
	check the DPoP proof according to the rules in <xref target="checking"></xref>,	check the DPoP proof according to the rules in <xref target="checking"></xref>,
	and check that the public key of the DPoP proof matches the public	and check that the public key of the DPoP proof matches the public
	key to which the access token is bound per <xref target="Confirmation"></xref>.< /t>	key to which the access token is bound per <xref target="Confirmation"></xref>.< /t>

	<t>The resource server MUST NOT grant access to the resource unless all	<t>The resource server <bcp14>MUST NOT</bcp14> grant access to the resource unle ss all
	checks are successful.</t>	checks are successful.</t>
	<t><xref target="protected-resource-request"></xref> shows an example request to a protected	<t><xref target="protected-resource-request"></xref> shows an example request to a protected
	resource with a DPoP-bound access token in the <tt>Authorization</tt> header	resource with a DPoP-bound access token in the <tt>Authorization</tt> header

	and the DPoP proof in the <tt>DPoP</tt> header	and the DPoP proof in the <tt>DPoP</tt> header.
	(with '\' line wrapping per RFC 8792).	The example uses "\" line wrapping per <xref target="RFC8792"/>.
	Following that is <xref target="dpop-proof-pr"></xref>, which shows the decoded	<xref target="dpop-proof-pr"></xref> shows the decoded content of that DPoP
	content of that DPoP	proof. The JSON of the JWT header and payload are shown,
	proof. The JSON of the JWT header and payload are shown
	but the signature part is omitted. As usual, line breaks and indentation	but the signature part is omitted. As usual, line breaks and indentation
	are included for formatting and readability.</t>	are included for formatting and readability.</t>

	<figure anchor="protected-resource-request"><name>DPoP Protected Resource Reques	<figure anchor="protected-resource-request"><name>DPoP-Protected Resource Reques
	t </name>	t </name>
	<artwork>GET /protectedresource HTTP/1.1	<sourcecode type="http-message">GET /protectedresource HTTP/1.1
	Host: resource.example.org	Host: resource.example.org
	Authorization: DPoP Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU	Authorization: DPoP Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU
	DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik\	DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik\
	VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR\	VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR\
	nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE\	nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE\
	QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiJlMWozVl9iS2ljOC1MQUVCIiwiaHRtIj\	QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiJlMWozVl9iS2ljOC1MQUVCIiwiaHRtIj\
	oiR0VUIiwiaHR1IjoiaHR0cHM6Ly9yZXNvdXJjZS5leGFtcGxlLm9yZy9wcm90ZWN0Z\	oiR0VUIiwiaHR1IjoiaHR0cHM6Ly9yZXNvdXJjZS5leGFtcGxlLm9yZy9wcm90ZWN0Z\
	WRyZXNvdXJjZSIsImlhdCI6MTU2MjI2MjYxOCwiYXRoIjoiZlVIeU8ycjJaM0RaNTNF\	WRyZXNvdXJjZSIsImlhdCI6MTU2MjI2MjYxOCwiYXRoIjoiZlVIeU8ycjJaM0RaNTNF\
	c05yV0JiMHhXWG9hTnk1OUlpS0NBcWtzbVFFbyJ9.2oW9RP35yRqzhrtNP86L-Ey71E\	c05yV0JiMHhXWG9hTnk1OUlpS0NBcWtzbVFFbyJ9.2oW9RP35yRqzhrtNP86L-Ey71E\
	OptxRimPPToA1plemAgR6pxHF8y6-yqyVnmcw6Fy1dqd-jfxSYoMxhAJpLjA	OptxRimPPToA1plemAgR6pxHF8y6-yqyVnmcw6Fy1dqd-jfxSYoMxhAJpLjA

	</artwork>	</sourcecode>
	</figure>	</figure>

	<figure anchor="dpop-proof-pr"><name>Decoded Content of the <tt>DPoP</tt> Proof	<figure anchor="dpop-proof-pr"><name>Decoded Content of the <tt>DPoP</tt> Proof
	JWT in <xref target="protected-resource-request"></xref> </name>	JWT in Figure 13</name>
	<artwork>{	<sourcecode type="json">{
	"typ":"dpop+jwt",	"typ":"dpop+jwt",
	"alg":"ES256",	"alg":"ES256",
	"jwk": {	"jwk": {
	"kty":"EC",	"kty":"EC",
	"x":"l8tFrhx-34tV3hRICRDY9zCkDlpBhF42UQUfWVAWBFs",	"x":"l8tFrhx-34tV3hRICRDY9zCkDlpBhF42UQUfWVAWBFs",
	"y":"9VE4jf_Ok_o64zbTTlcuNJajHmt6v9TDVrU0CdvGRDA",	"y":"9VE4jf_Ok_o64zbTTlcuNJajHmt6v9TDVrU0CdvGRDA",
	"crv":"P-256"	"crv":"P-256"
	}	}
	}	}
	.	.
	{	{

	"jti":"e1j3V_bKic8-LAEB",	"jti":"e1j3V_bKic8-LAEB",
	"htm":"GET",	"htm":"GET",
	"htu":"https://resource.example.org/protectedresource",	"htu":"https://resource.example.org/protectedresource",
	"iat":1562262618,	"iat":1562262618,
	"ath":"fUHyO2r2Z3DZ53EsNrWBb0xWXoaNy59IiKCAqksmQEo"	"ath":"fUHyO2r2Z3DZ53EsNrWBb0xWXoaNy59IiKCAqksmQEo"
	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>

	<t>Upon receipt of a request to a protected resource within	<t>Upon receipt of a request to a protected resource within the protection
	the protection space requiring DPoP authentication, if the request does	space requiring DPoP authentication, the server can respond with a challenge
	not include valid credentials or does not contain an access	to the client to provide DPoP authentication information if the request does
	token sufficient for access, the server	not include valid credentials or does not contain an access token sufficient
	can respond with a challenge to the client to provide DPoP authentication inform	for access. Such a challenge is made using the 401 (Unauthorized) response
	ation.	status code (<xref target="RFC9110" sectionFormat="comma"
	Such a challenge is made using the 401 (Unauthorized) response status code	section="15.5.2"></xref>) and the <tt>WWW-Authenticate</tt> header field
	(<xref target="RFC9110"></xref>, Section 15.5.2) and the <tt>WWW-Authenticate</t	(<xref target="RFC9110" sectionFormat="comma" section="11.6.1"></xref>). The
	t> header field	server <bcp14>MAY</bcp14> include the <tt>WWW-Authenticate</tt> header in
	(<xref target="RFC9110"></xref>, Section 11.6.1). The server MAY include the	response to other conditions as well.</t>
	<tt>WWW-Authenticate</tt> header in response to other conditions as well.</t>
	<t>In such challenges:</t>	<t>In such challenges:</t>

	<ul spacing="compact">	<ul spacing="compact">
	<li>The scheme name is <tt>DPoP</tt>.</li>	<li>The scheme name is <tt>DPoP</tt>.</li>

	<li>The authentication parameter <tt>realm</tt> MAY be included to indicate the	<li>The authentication parameter <tt>realm</tt> <bcp14>MAY</bcp14> be included t
	scope of protection in the manner described in <xref target="RFC9110"></xref>, S	o indicate the
	ection 11.5.</li>	scope of protection in the manner described in <xref target="RFC9110" sectionFor
	<li>A <tt>scope</tt> authentication parameter MAY be included as defined in	mat="comma" section="11.5"></xref>.</li>
	<xref target="RFC6750"></xref>, Section 3.</li>	<li>A <tt>scope</tt> authentication parameter <bcp14>MAY</bcp14> be included as
	<li>An <tt>error</tt> parameter (<xref target="RFC6750"></xref>, Section 3) SHOU	defined in
	LD be included	<xref target="RFC6750" sectionFormat="comma" section="3"></xref>.</li>
		<li>An <tt>error</tt> parameter (<xref target="RFC6750" sectionFormat="comma" se
		ction="3"></xref>) <bcp14>SHOULD</bcp14> be included
	to indicate the reason why the request was declined,	to indicate the reason why the request was declined,
	if the request included an access token but failed authentication.	if the request included an access token but failed authentication.

	The error parameter values described in Section 3.1 of <xref target="RFC6750"></ xref> are suitable	The error parameter values described in <xref target="RFC6750" sectionFormat="co mma" section="3.1"></xref> are suitable,
	as are any appropriate values defined by extension. The value <tt>use_dpop_nonce </tt> can be	as are any appropriate values defined by extension. The value <tt>use_dpop_nonce </tt> can be

	used as described in <xref target="RSNonce"></xref> to signal that a nonce is ne	used as described in <xref target="RSNonce"></xref> to signal that a nonce is ne
	eded in the DPoP proof of	eded in the DPoP proof of a
	subsequent request(s). And <tt>invalid_dpop_proof</tt> is used to indicate that	subsequent request(s). Additionally, <tt>invalid_dpop_proof</tt> is used to indi
	the DPoP proof	cate that the DPoP proof
	itself was deemed invalid based on the criteria of <xref target="checking"></xre f>.</li>	itself was deemed invalid based on the criteria of <xref target="checking"></xre f>.</li>

	<li>An <tt>error_description</tt> parameter (<xref target="RFC6750"></xref>, Sec tion 3) MAY be included	<li>An <tt>error_description</tt> parameter (<xref target="RFC6750" sectionForma t="comma" section="3"></xref>) <bcp14>MAY</bcp14> be included
	along with the <tt>error</tt> parameter to provide developers a human-readable	along with the <tt>error</tt> parameter to provide developers a human-readable
	explanation that is not meant to be displayed to end-users.</li>	explanation that is not meant to be displayed to end-users.</li>

	<li>An <tt>algs</tt> parameter SHOULD be included to signal to the client the	<li>An <tt>algs</tt> parameter <bcp14>SHOULD</bcp14> be included to signal to th e client the
	JWS algorithms that are acceptable for the DPoP proof JWT.	JWS algorithms that are acceptable for the DPoP proof JWT.
	The value of the parameter is a space-delimited list of JWS <tt>alg</tt> (Algori thm)	The value of the parameter is a space-delimited list of JWS <tt>alg</tt> (Algori thm)

	header values (<xref target="RFC7515"></xref>, Section 4.1.1).</li>	header values (<xref target="RFC7515" sectionFormat="comma" section="4.1.1"></xr
	<li>Additional authentication parameters MAY be used and unknown parameters	ef>).</li>
	MUST be ignored by recipients.</li>	<li>Additional authentication parameters <bcp14>MAY</bcp14> be used, and unknown
		parameters
		<bcp14>MUST</bcp14> be ignored by recipients.</li>
	</ul>	</ul>

	<t>For example, in response to a protected resource request without	<t><xref target="http-401-response-protected-req-without-auth"/> shows a respons
	authentication:</t>	e to a protected resource request without
	<figure><name>HTTP 401 Response to a Protected Resource Request without Authenti	authentication.</t>
	cation	<figure anchor="http-401-response-protected-req-without-auth"><name>HTTP 401 Res
		ponse to a Protected Resource Request without Authentication
	</name>	</name>

	<artwork> HTTP/1.1 401 Unauthorized	<sourcecode type="http-message"> HTTP/1.1 401 Unauthorized
	WWW-Authenticate: DPoP algs="ES256 PS256"	WWW-Authenticate: DPoP algs="ES256 PS256"
	</artwork>	</sourcecode>
	</figure>	</figure>

	<t>And in response to a protected resource request that was rejected	<t><xref target="http-401-response-protected-req-with-invalid-token"/> shows a r
	because the confirmation of the DPoP binding in the access token failed	esponse to a protected resource request that was rejected
	(with '\' line wrapping per RFC 8792):</t>	due to the failed confirmation of the DPoP binding in the access token. <xref ta
	<figure><name>HTTP 401 Response to a Protected Resource Request with an Invalid	rget="http-401-response-protected-req-with-invalid-token"/>
	Token	uses "\" line wrapping per <xref target="RFC8792"/>.</t>
		<figure anchor="http-401-response-protected-req-with-invalid-token"><name>HTTP 4
		01 Response to a Protected Resource Request with an Invalid Token
	</name>	</name>

	<artwork> HTTP/1.1 401 Unauthorized	<sourcecode type="http-message">
	WWW-Authenticate: DPoP error="invalid_token", \	HTTP/1.1 401 Unauthorized
	error_description="Invalid DPoP key binding", algs="ES256&quot	WWW-Authenticate: DPoP error="invalid_token", \
	;	error_description="Invalid DPoP key binding", algs="ES256"
	</artwork>	</sourcecode>
	</figure>	</figure>

	<t>Note that browser-based client applications using CORS <xref target="WHATWG.F etch"></xref> only have access	<t>Note that browser-based client applications using Cross-Origin Resource Shari ng (CORS) <xref target="WHATWG.Fetch"></xref> only have access
	to CORS-safelisted response HTTP headers by default.	to CORS-safelisted response HTTP headers by default.
	In order for the application to obtain and use the <tt>WWW-Authenticate</tt> HTT P response header	In order for the application to obtain and use the <tt>WWW-Authenticate</tt> HTT P response header
	value, the server needs to make it available to the application by including	value, the server needs to make it available to the application by including
	<tt>WWW-Authenticate</tt> in the <tt>Access-Control-Expose-Headers</tt> response header list value.</t>	<tt>WWW-Authenticate</tt> in the <tt>Access-Control-Expose-Headers</tt> response header list value.</t>
	<t>This authentication scheme is for origin-server authentication only.	<t>This authentication scheme is for origin-server authentication only.

	Therefore, this authentication scheme MUST NOT be used with the	Therefore, this authentication scheme <bcp14>MUST NOT</bcp14> be used with the
	<tt>Proxy-Authenticate</tt> or <tt>Proxy-Authorization</tt> header fields.</t>	<tt>Proxy-Authenticate</tt> or <tt>Proxy-Authorization</tt> header fields.</t>
	<t>Note that the syntax of the <tt>Authorization</tt> header field for this auth entication scheme	<t>Note that the syntax of the <tt>Authorization</tt> header field for this auth entication scheme

	follows the usage of the <tt>Bearer</tt> scheme defined in Section 2.1 of <xref	follows the usage of the <tt>Bearer</tt> scheme defined in <xref target="RFC6750
	target="RFC6750"></xref>.	" sectionFormat="of" section="2.1"></xref>.
	While not the preferred credential syntax of <xref target="RFC9110"></xref>, it	While it is not the preferred credential syntax of <xref target="RFC9110"></xref
	is compatible	>, it is compatible
	with the general authentication framework therein and was used for consistency	with the general authentication framework therein and is used for consistency
	and familiarity with the <tt>Bearer</tt> scheme.</t>	and familiarity with the <tt>Bearer</tt> scheme.</t>
	</section>	</section>

	<section anchor="compatibility-with-the-bearer-authentication-scheme"><name>Comp atibility with the Bearer Authentication Scheme</name>	<section anchor="compatibility-with-the-bearer-authentication-scheme"><name>Comp atibility with the Bearer Authentication Scheme</name>
	<t>Protected resources simultaneously supporting both the <tt>DPoP</tt> and <tt> Bearer</tt>	<t>Protected resources simultaneously supporting both the <tt>DPoP</tt> and <tt> Bearer</tt>

	schemes need to update how evaluation of bearer tokens is performed to prevent	schemes need to update how the evaluation process is performed for bearer tokens to prevent
	downgraded usage of a DPoP-bound access token.	downgraded usage of a DPoP-bound access token.

	Specifically, such a protected resource MUST reject a DPoP-bound access	Specifically, such a protected resource <bcp14>MUST</bcp14> reject a DPoP-bound access
	token received as a bearer token per <xref target="RFC6750"></xref>.</t>	token received as a bearer token per <xref target="RFC6750"></xref>.</t>

	<t>Section 11.6.1 of <xref target="RFC9110"></xref> allows a protected resource to indicate support for	<t><xref target="RFC9110" sectionFormat="of" section="11.6.1"></xref> allows a p rotected resource to indicate support for
	multiple authentication schemes (i.e., <tt>Bearer</tt> and <tt>DPoP</tt>) with t he	multiple authentication schemes (i.e., <tt>Bearer</tt> and <tt>DPoP</tt>) with t he
	<tt>WWW-Authenticate</tt> header field of a 401 (Unauthorized) response.</t>	<tt>WWW-Authenticate</tt> header field of a 401 (Unauthorized) response.</t>
	<t>A protected resource that supports only <xref target="RFC6750"></xref> and is unaware of DPoP	<t>A protected resource that supports only <xref target="RFC6750"></xref> and is unaware of DPoP
	would most presumably accept a DPoP-bound access token as a bearer token	would most presumably accept a DPoP-bound access token as a bearer token
	(JWT <xref target="RFC7519"></xref> says to ignore unrecognized claims, Introspe ction <xref target="RFC7662"></xref>	(JWT <xref target="RFC7519"></xref> says to ignore unrecognized claims, Introspe ction <xref target="RFC7662"></xref>
	says that other parameters might be present while placing no functional	says that other parameters might be present while placing no functional
	requirements on their presence, and <xref target="RFC6750"></xref> is effectivel y silent on	requirements on their presence, and <xref target="RFC6750"></xref> is effectivel y silent on

	the content of the access token as it relates to validity). As such, a	the content of the access token since it relates to validity).
		As such, a
	client can send a DPoP-bound access token using the <tt>Bearer</tt> scheme upon	client can send a DPoP-bound access token using the <tt>Bearer</tt> scheme upon
	receipt of a <tt>WWW-Authenticate: Bearer</tt> challenge from a protected resour ce	receipt of a <tt>WWW-Authenticate: Bearer</tt> challenge from a protected resour ce

	(or if it has prior such knowledge about the capabilities of the protected	(or it can send a DPoP-bound access token if it has prior knowledge of the capab ilities of the protected
	resource). The effect of this likely simplifies the logistics of phased	resource). The effect of this likely simplifies the logistics of phased

	upgrades to protected resources in their support DPoP or even	upgrades to protected resources in their support DPoP or
	prolonged deployments of protected resources with mixed token type support.</t>	prolonged deployments of protected resources with mixed token type support.</t>
	<t>If a protected resource supporting both <tt>Bearer</tt> and <tt>DPoP</tt> sch emes elects to	<t>If a protected resource supporting both <tt>Bearer</tt> and <tt>DPoP</tt> sch emes elects to
	respond with multiple <tt>WWW-Authenticate</tt> challenges, attention should be paid to	respond with multiple <tt>WWW-Authenticate</tt> challenges, attention should be paid to
	which challenge(s) should deliver the actual error information. It is	which challenge(s) should deliver the actual error information. It is

	RECOMMENDED that the following rules be adhered to:</t>	<bcp14>RECOMMENDED</bcp14> that the following rules be adhered to:</t>

	<ul>	<ul>
	<li><t>If no authentication information has been included with the request, then the	<li><t>If no authentication information has been included with the request, then the

	challenges SHOULD NOT include an error code or other error information, as per	challenges <bcp14>SHOULD NOT</bcp14> include an error code or other error inform
	<xref target="RFC6750"></xref>, Section 3.1 (<xref target="multi-challenge-no-to	ation, as per
	ken"></xref>).</t>	<xref target="RFC6750" sectionFormat="of" section="3.1"></xref> (<xref target="m
		ulti-challenge-no-token"></xref>).</t>
	</li>	</li>
	<li><t>If the mechanism used to attempt authentication could be established	<li><t>If the mechanism used to attempt authentication could be established

	unambiguously, then the corresponding challenge SHOULD be used to deliver error	unambiguously, then the corresponding challenge <bcp14>SHOULD</bcp14> be used to deliver error
	information (<xref target="multi-challenge-invalid-token"></xref>).</t>	information (<xref target="multi-challenge-invalid-token"></xref>).</t>
	</li>	</li>

	<li><t>Otherwise, both <tt>Bearer</tt> and <tt>DPoP</tt> challenged MAY be used	<li><t>Otherwise, both <tt>Bearer</tt> and <tt>DPoP</tt> challenges <bcp14>MAY</
	to deliver error	bcp14> be used to deliver error information (<xref target="multi-challenge-ambig
	information (<xref target="multi-challenge-ambiguous"></xref>).</t>	uous"></xref>).</t>
	</li>	</li>
	</ul>	</ul>

	<t>(Where needed, the following examples use '\' line wrapping per RFC 8792.)</t >	<t>The following examples use "\" line wrapping per <xref target="RFC8792"/>.</t >
	<figure anchor="multi-challenge-no-token"><name>HTTP 401 Response to a Protected Resource Request without Authentication </name>	<figure anchor="multi-challenge-no-token"><name>HTTP 401 Response to a Protected Resource Request without Authentication </name>

	<artwork>GET /protectedresource HTTP/1.1	<sourcecode type="http-message">GET /protectedresource HTTP/1.1
	Host: resource.example.org	Host: resource.example.org

	HTTP/1.1 401 Unauthorized	HTTP/1.1 401 Unauthorized

	WWW-Authenticate: Bearer, DPoP algs="ES256 PS256"	WWW-Authenticate: Bearer, DPoP algs="ES256 PS256"
	</artwork>	</sourcecode>
	</figure>	</figure>
	<figure anchor="multi-challenge-invalid-token"><name>HTTP 401 Response to a Prot ected Resource Request with Invalid Authentication </name>	<figure anchor="multi-challenge-invalid-token"><name>HTTP 401 Response to a Prot ected Resource Request with Invalid Authentication </name>

	<artwork>GET /protectedresource HTTP/1.1	<sourcecode type="http-message">GET /protectedresource HTTP/1.1
	Host: resource.example.org	Host: resource.example.org
	Authorization: Bearer INVALID_TOKEN	Authorization: Bearer INVALID_TOKEN

	HTTP/1.1 401 Unauthorized	HTTP/1.1 401 Unauthorized

	WWW-Authenticate: Bearer error="invalid_token", \	WWW-Authenticate: Bearer error="invalid_token", \
	error_description="Invalid token", DPoP algs="ES256 PS256&quo	error_description="Invalid token", DPoP algs="ES256 PS256"
	t;	</sourcecode>
	</artwork>
	</figure>	</figure>
	<figure anchor="multi-challenge-ambiguous"><name>HTTP 400 Response to a Protecte d Resource Request with Ambiguous Authentication </name>	<figure anchor="multi-challenge-ambiguous"><name>HTTP 400 Response to a Protecte d Resource Request with Ambiguous Authentication </name>

	<artwork>GET /protectedresource HTTP/1.1	<sourcecode type="http-message">GET /protectedresource HTTP/1.1
	Host: resource.example.org	Host: resource.example.org
	Authorization: Bearer Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU	Authorization: Bearer Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU
	Authorization: DPoP Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU	Authorization: DPoP Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU

	HTTP/1.1 400 Bad Request	HTTP/1.1 400 Bad Request

	WWW-Authenticate: Bearer error="invalid_request", \	WWW-Authenticate: Bearer error="invalid_request", \
	error_description="Multiple methods used to include access token", \	error_description="Multiple methods used to include access token", \
	DPoP algs="ES256 PS256", error="invalid_request", \	DPoP algs="ES256 PS256", error="invalid_request", \
	error_description="Multiple methods used to include access token"	error_description="Multiple methods used to include access token"
	</artwork>	</sourcecode>
	</figure>	</figure>
	</section>	</section>

	<section anchor="client-considerations"><name>Client Considerations</name>	<section anchor="client-considerations"><name>Client Considerations</name>
	<t>Authorization including a DPoP proof may not be idempotent (depending on serv er	<t>Authorization including a DPoP proof may not be idempotent (depending on serv er

	enforcement of <tt>jti</tt>, <tt>iat</tt> and <tt>nonce</tt> claims). Consequent ly, all previously	enforcement of <tt>jti</tt>, <tt>iat</tt>, and <tt>nonce</tt> claims). Consequen tly, all previously
	idempotent requests for protected resources that were previously idempotent may	idempotent requests for protected resources that were previously idempotent may

	no longer be idempotent. It is RECOMMENDED that clients generate a unique DPoP	no longer be idempotent. It is <bcp14>RECOMMENDED</bcp14> that clients generate
	proof even when retrying idempotent requests in response to HTTP errors	a unique DPoP
		proof, even when retrying idempotent requests in response to HTTP errors
	generally understood as transient.</t>	generally understood as transient.</t>
	<t>Clients that encounter frequent network errors may experience additional	<t>Clients that encounter frequent network errors may experience additional

	challenges when interacting with servers with more strict nonce validation	challenges when interacting with servers with stricter nonce validation
	implementations.</t>	implementations.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="ASNonce"><name>Authorization Server-Provided Nonce</name>	<section anchor="ASNonce"><name>Authorization Server-Provided Nonce</name>
	<t>This section specifies a mechanism using opaque nonces provided by the server	<t>This section specifies a mechanism using opaque nonces provided by the server
	that can be used to limit the lifetime of DPoP proofs.	that can be used to limit the lifetime of DPoP proofs.
	Without employing such a mechanism, a malicious party controlling the client	Without employing such a mechanism, a malicious party controlling the client

	(including potentially the end-user)	(potentially including the end-user)
	can create DPoP proofs for use arbitrarily far in the future.</t>	can create DPoP proofs for use arbitrarily far in the future.</t>
	<t>Including a nonce value contributed by the authorization server in the DPoP p roof	<t>Including a nonce value contributed by the authorization server in the DPoP p roof

	MAY be used by authorization servers to limit the lifetime of DPoP proofs.	<bcp14>MAY</bcp14> be used by authorization servers to limit the lifetime of DPo
	The server determines when and if to issue a new DPoP nonce challenge	P proofs.
	thereby requiring the use of the nonce value in subsequent DPoP proofs.	The server determines when to issue a new DPoP nonce challenge and if
		it is needed, thereby requiring the use of the nonce value in
		subsequent DPoP proofs.
	The logic through which the server makes that determination is out of scope of t his document.</t>	The logic through which the server makes that determination is out of scope of t his document.</t>

	<t>An authorization server MAY supply a nonce value to be included by the client	<t>An authorization server <bcp14>MAY</bcp14> supply a nonce value to be include
	in DPoP proofs sent. In this case, the authorization server responds to requests	d by the client
	not including a nonce	in DPoP proofs sent. In this case, the authorization server responds to requests
	with an HTTP <tt>400</tt> (Bad Request) error response per Section 5.2 of <xref	that do not include a nonce
	target="RFC6749"></xref> using <tt>use_dpop_nonce</tt> as the	with an HTTP 400 (Bad Request) error response per <xref target="RFC6749" section
		Format="of" section="5.2"></xref> using <tt>use_dpop_nonce</tt> as the
	error code value. The authorization server includes a <tt>DPoP-Nonce</tt> HTTP h eader in the response supplying	error code value. The authorization server includes a <tt>DPoP-Nonce</tt> HTTP h eader in the response supplying

	a nonce value to be used when sending the subsequent request. Nonce values MUST be unpredictable.	a nonce value to be used when sending the subsequent request. Nonce values <bcp1 4>MUST</bcp14> be unpredictable.
	This same error code is used when supplying a new nonce value when there was a n once mismatch.	This same error code is used when supplying a new nonce value when there was a n once mismatch.
	The client will typically retry the request with the new nonce value supplied	The client will typically retry the request with the new nonce value supplied
	upon receiving a <tt>use_dpop_nonce</tt> error with an accompanying nonce value. </t>	upon receiving a <tt>use_dpop_nonce</tt> error with an accompanying nonce value. </t>
	<t>For example, in response to a token request without a nonce when the authoriz ation server requires one,	<t>For example, in response to a token request without a nonce when the authoriz ation server requires one,
	the authorization server can respond with a <tt>DPoP-Nonce</tt> value such as th e following to provide	the authorization server can respond with a <tt>DPoP-Nonce</tt> value such as th e following to provide
	a nonce value to include in the DPoP proof:</t>	a nonce value to include in the DPoP proof:</t>

	<figure><name>HTTP 400 Response to a Token Request without a Nonce	<figure anchor="http-400-response-token-without-nonce"><name>HTTP 400 Response t o a Token Request without a Nonce
	</name>	</name>

	<artwork> HTTP/1.1 400 Bad Request	<sourcecode type="http-message"> HTTP/1.1 400 Bad Request
	DPoP-Nonce: eyJ7S_zG.eyJH0-Z.HX4w-7v	DPoP-Nonce: eyJ7S_zG.eyJH0-Z.HX4w-7v

	{	{

	"error": "use_dpop_nonce",	"error": "use_dpop_nonce",
	"error_description":	"error_description":
	"Authorization server requires nonce in DPoP proof"	"Authorization server requires nonce in DPoP proof"
	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>

	<t>Other HTTP headers and JSON fields MAY also be included in the error response	<t>Other HTTP headers and JSON fields <bcp14>MAY</bcp14> also be included in the
	,	error response,
	but there MUST NOT be more than one <tt>DPoP-Nonce</tt> header.</t>	but there <bcp14>MUST NOT</bcp14> be more than one <tt>DPoP-Nonce</tt> header.</
		t>
	<t>Upon receiving the nonce, the client is expected to retry its token request	<t>Upon receiving the nonce, the client is expected to retry its token request
	using a DPoP proof including the supplied nonce value in the <tt>nonce</tt> clai m	using a DPoP proof including the supplied nonce value in the <tt>nonce</tt> clai m
	of the DPoP proof.	of the DPoP proof.

	An example unencoded JWT Payload of such a DPoP proof including a nonce is:</t>	An example unencoded JWT payload of such a DPoP proof including a nonce is shown
	<figure><name>DPoP Proof Payload Including a Nonce Value	below.</t>
		<figure anchor="dpop-proof-payload-nonce-value"><name>DPoP Proof Payload includi
		ng a Nonce Value
	</name>	</name>

	<artwork> {	<sourcecode type="json"> {
	"jti": "-BwC3ESc6acc2lTc",	"jti": "-BwC3ESc6acc2lTc",
	"htm": "POST",	"htm": "POST",
	"htu": "https://server.example.com/token",	"htu": "https://server.example.com/token",
	"iat": 1562262616,	"iat": 1562262616,
	"nonce": "eyJ7S_zG.eyJH0-Z.HX4w-7v"	"nonce": "eyJ7S_zG.eyJH0-Z.HX4w-7v"
	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>
	<t>The nonce is opaque to the client.</t>	<t>The nonce is opaque to the client.</t>
	<t>If the <tt>nonce</tt> claim in the DPoP proof	<t>If the <tt>nonce</tt> claim in the DPoP proof
	does not exactly match a nonce recently supplied by the authorization server to the client,	does not exactly match a nonce recently supplied by the authorization server to the client,

	the authorization server MUST reject the request.	the authorization server <bcp14>MUST</bcp14> reject the request.
	The rejection response MAY include a <tt>DPoP-Nonce</tt> HTTP header	The rejection response <bcp14>MAY</bcp14> include a <tt>DPoP-Nonce</tt> HTTP hea
		der
	providing a new nonce value to use for subsequent requests.</t>	providing a new nonce value to use for subsequent requests.</t>

	<t>The intent is that clients need to keep only one nonce value and servers keep
	a	<t>The intent is that clients need to keep only one nonce value and servers need
		to keep a
	window of recent nonces.	window of recent nonces.

	That said, transient circumstances may arise in which the server's and client's	That said, transient circumstances may arise in which the
	stored nonce values differ.	stored nonce values for the server and the client differ.
	However, this situation is self-correcting;	However, this situation is self-correcting.
	with any rejection message,	With any rejection message,
	the server can send the client the nonce value that the server wants it to use	the server can send the client the nonce value it wants to use
	and the client can store that nonce value and retry the request with it.	to the client, and the client can store that nonce value and retry the request w
		ith it.
	Even if the client and/or server discard their stored nonce values,	Even if the client and/or server discard their stored nonce values,
	that situation is also self-correcting because new nonce values can be communica ted	that situation is also self-correcting because new nonce values can be communica ted
	when responding to or retrying failed requests.</t>	when responding to or retrying failed requests.</t>
	<t>Note that browser-based client applications using CORS <xref target="WHATWG.F etch"></xref> only have access	<t>Note that browser-based client applications using CORS <xref target="WHATWG.F etch"></xref> only have access
	to CORS-safelisted response HTTP headers by default.	to CORS-safelisted response HTTP headers by default.
	In order for the application to obtain and use the <tt>DPoP-Nonce</tt> HTTP resp onse header	In order for the application to obtain and use the <tt>DPoP-Nonce</tt> HTTP resp onse header
	value, the server needs to make it available to the application by including	value, the server needs to make it available to the application by including
	<tt>DPoP-Nonce</tt> in the <tt>Access-Control-Expose-Headers</tt> response heade r list value.</t>	<tt>DPoP-Nonce</tt> in the <tt>Access-Control-Expose-Headers</tt> response heade r list value.</t>

	<section anchor="NonceSyntax"><name>Nonce Syntax</name>	<section anchor="NonceSyntax"><name>Nonce Syntax</name>
	<t>The nonce syntax in ABNF as used by <xref target="RFC6749"></xref>	<t>The nonce syntax in ABNF as used by <xref target="RFC6749"></xref>

	(which is the same as the <tt>scope-token</tt> syntax) is:</t>	(which is the same as the scope-token syntax) is shown below.</t>
	<figure><name>Nonce ABNF	<figure anchor="nonce-abnf"><name>Nonce ABNF
	</name>	</name>

	<artwork> nonce = 1*NQCHAR	<sourcecode type="abnf"><![CDATA[nonce = 1*NQCHAR]]></sourcecode>
	</artwork>
	</figure>	</figure>
	</section>	</section>

	<section anchor="NewNonce"><name>Providing a New Nonce Value</name>	<section anchor="NewNonce"><name>Providing a New Nonce Value</name>
	<t>It is up to the authorization server when to supply a new nonce value	<t>It is up to the authorization server when to supply a new nonce value
	for the client to use.	for the client to use.
	The client is expected to use the existing supplied nonce in DPoP proofs	The client is expected to use the existing supplied nonce in DPoP proofs
	until the server supplies a new nonce value.</t>	until the server supplies a new nonce value.</t>

	<t>The authorization server MAY supply the new nonce in the same way that	<t>The authorization server <bcp14>MAY</bcp14> supply the new nonce in the same
	the initial one was supplied:	way that
	by using a <tt>DPoP-Nonce</tt> HTTP header in the response.	the initial one was supplied: by using a <tt>DPoP-Nonce</tt> HTTP header in the
		response.
	The <tt>DPoP-Nonce</tt> HTTP header field uses the nonce syntax defined in <xref target="NonceSyntax"></xref>.	The <tt>DPoP-Nonce</tt> HTTP header field uses the nonce syntax defined in <xref target="NonceSyntax"></xref>.

	Of course, each time this happens it requires an extra protocol round trip.</t>	Each time this happens, it requires an extra protocol round trip.</t>
	<t>A more efficient manner of supplying a new nonce value is also defined --	<t>A more efficient manner of supplying a new nonce value is also defined
	by including a <tt>DPoP-Nonce</tt> HTTP header	by including a <tt>DPoP-Nonce</tt> HTTP header

	in the HTTP <tt>200</tt> (OK) response from the previous request.	in the HTTP 200 (OK) response from the previous request.
	The client MUST use the new nonce value supplied for the next token request,	The client <bcp14>MUST</bcp14> use the new nonce value supplied for the next tok
		en request
	and for all subsequent token requests until the authorization server	and for all subsequent token requests until the authorization server
	supplies a new nonce.</t>	supplies a new nonce.</t>
	<t>Responses that include the <tt>DPoP-Nonce</tt> HTTP header should be uncachea ble	<t>Responses that include the <tt>DPoP-Nonce</tt> HTTP header should be uncachea ble
	(e.g., using <tt>Cache-Control: no-store</tt> in response to a <tt>GET</tt> requ est) to	(e.g., using <tt>Cache-Control: no-store</tt> in response to a <tt>GET</tt> requ est) to

	prevent the response being used to serve a subsequent request and a stale	prevent the response from being used to serve a subsequent request and a stale
	nonce value being used as a result.</t>	nonce value from being used as a result.</t>
	<t>An example 200 OK response providing a new nonce value is:</t>	<t>An example 200 OK response providing a new nonce value is shown below.</t>
	<figure><name>HTTP 200 Response Providing the Next Nonce Value	<figure anchor="http-200-response-next-nonce-value"><name>HTTP 200 Response Prov
		iding the Next Nonce Value
	</name>	</name>

	<artwork> HTTP/1.1 200 OK	<sourcecode type="http-message"> HTTP/1.1 200 OK
	Cache-Control: no-store	Cache-Control: no-store
	DPoP-Nonce: eyJ7S_zG.eyJbYu3.xQmBj-1	DPoP-Nonce: eyJ7S_zG.eyJbYu3.xQmBj-1

	</artwork>	</sourcecode>
	</figure>	</figure>
	</section>	</section>
	</section>	</section>

	<section anchor="RSNonce"><name>Resource Server-Provided Nonce</name>	<section anchor="RSNonce"><name>Resource Server-Provided Nonce</name>
	<t>Resource servers can also choose to provide a nonce value to be included	<t>Resource servers can also choose to provide a nonce value to be included
	in DPoP proofs sent to them.	in DPoP proofs sent to them.
	They provide the nonce using the <tt>DPoP-Nonce</tt> header in the same way that authorization servers do	They provide the nonce using the <tt>DPoP-Nonce</tt> header in the same way that authorization servers do

	as described in <xref target="ASNonce"></xref> and <xref target="NewNonce"></xre f>.	as described in Sections <xref target="ASNonce" format="counter"></xref> and <xr ef target="NewNonce" format="counter"></xref>.
	The error signaling is performed as described in <xref target="http-auth-scheme" ></xref>.	The error signaling is performed as described in <xref target="http-auth-scheme" ></xref>.

	Resource servers use an HTTP <tt>401</tt> (Unauthorized) error code	Resource servers use an HTTP 401 (Unauthorized) error code
	with an accompanying <tt>WWW-Authenticate: DPoP</tt> value	with an accompanying <tt>WWW-Authenticate: DPoP</tt> value
	and <tt>DPoP-Nonce</tt> value to accomplish this.</t>	and <tt>DPoP-Nonce</tt> value to accomplish this.</t>
	<t>For example, in response to a resource request without a nonce when the resou rce server requires one,	<t>For example, in response to a resource request without a nonce when the resou rce server requires one,
	the resource server can respond with a <tt>DPoP-Nonce</tt> value such as the fol lowing to provide	the resource server can respond with a <tt>DPoP-Nonce</tt> value such as the fol lowing to provide

	a nonce value to include in the DPoP proof	a nonce value to include in the DPoP proof.
	(with '\' line wrapping per RFC 8792):</t>	The example below uses "\" line wrapping per <xref target="RFC8792"/>.</t>
	<figure><name>HTTP 401 Response to a Resource Request without a Nonce	<figure anchor="http-401-response-resource-request-without-nonce"><name>HTTP 401
		Response to a Resource Request without a Nonce
	</name>	</name>

	<artwork> HTTP/1.1 401 Unauthorized	<sourcecode type="http-message"> HTTP/1.1 401 Unauthorized
	WWW-Authenticate: DPoP error="use_dpop_nonce", \	WWW-Authenticate: DPoP error="use_dpop_nonce", \
	error_description="Resource server requires nonce in DPoP proof"	error_description="Resource server requires nonce in DPoP proof"
	DPoP-Nonce: eyJ7S_zG.eyJH0-Z.HX4w-7v	DPoP-Nonce: eyJ7S_zG.eyJH0-Z.HX4w-7v

	</artwork>	</sourcecode>
	</figure>	</figure>
	<t>Note that the nonces provided by an authorization server and a resource serve r are different	<t>Note that the nonces provided by an authorization server and a resource serve r are different

	and should not be confused with one another,	and should not be confused with one another
	since nonces will be only accepted by the server that issued them.	since nonces will be only accepted by the server that issued them.
	Likewise, should a client use multiple authorization servers and/or resource ser vers,	Likewise, should a client use multiple authorization servers and/or resource ser vers,
	a nonce issued by any of them should be used only at the issuing server.	a nonce issued by any of them should be used only at the issuing server.

	Developers should also take care to not confuse DPoP nonces with the	Developers should also be careful to not confuse DPoP nonces with the
	OpenID Connect <xref target="OpenID.Core"></xref> ID Token nonce.</t>	OpenID Connect <xref target="OpenID.Core"></xref> ID Token nonce.</t>
	</section>	</section>


	<section anchor="dpop_jkt"><name>Authorization Code Binding to DPoP Key</name>	<section anchor="dpop_jkt"><name>Authorization Code Binding to a DPoP Key</name>
	<t>Binding the authorization code issued to the client's proof-of-possession key	<t>Binding the authorization code issued to the client's proof-of-possession key
	can enable end-to-end binding of the entire authorization flow.	can enable end-to-end binding of the entire authorization flow.
	This specification defines the <tt>dpop_jkt</tt> authorization request parameter for this purpose.	This specification defines the <tt>dpop_jkt</tt> authorization request parameter for this purpose.
	The value of the <tt>dpop_jkt</tt> authorization request parameter is the	The value of the <tt>dpop_jkt</tt> authorization request parameter is the

	JSON Web Key (JWK) Thumbprint <xref target="RFC7638"></xref> of the proof-of-pos	JWK Thumbprint <xref target="RFC7638"></xref> of the proof-of-possession public
	session public key	key
	using the SHA-256 hash function -	using the SHA-256 hash function, which is
	the same value as used for the <tt>jkt</tt> confirmation method defined in <xref target="jwk-thumb-jwt"></xref>.</t>	the same value as used for the <tt>jkt</tt> confirmation method defined in <xref target="jwk-thumb-jwt"></xref>.</t>
	<t>When a token request is received, the authorization server computes the	<t>When a token request is received, the authorization server computes the

	JWK thumbprint of the proof-of-possession public key in the DPoP proof	JWK Thumbprint of the proof-of-possession public key in the DPoP proof
	and verifies that it matches the <tt>dpop_jkt</tt> parameter value in the author ization request.	and verifies that it matches the <tt>dpop_jkt</tt> parameter value in the author ization request.

	If they do not match, it MUST reject the request.</t>	If they do not match, it <bcp14>MUST</bcp14> reject the request.</t>
	<t>An example authorization request using the <tt>dpop_jkt</tt> authorization re	<t>An example authorization request using the <tt>dpop_jkt</tt> authorization re
	quest parameter follows	quest parameter is shown below and uses "\" line wrapping per <xref target="RFC8
	(with '\' line wrapping per RFC 8792):</t>	792"/>.</t>
	<figure><name>Authorization Request using the <tt>dpop_jkt</tt> Parameter	<figure anchor="auth-req-using-dpopjkt-parameter"><name>Authorization Request Us
		ing the <tt>dpop_jkt</tt> Parameter
	</name>	</name>

	<artwork> GET /authorize?response_type=code&client_id=s6BhdRkqt3&state=x	<sourcecode type="http-message"><![CDATA[
	yz\	GET /authorize?response_type=code&client_id=s6BhdRkqt3&state=xyz\
	&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb\	&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb\
	&code_challenge=E9Melhoa2OwvFrEMTJguCHaoeK1t8URWbuGJSstw-cM\	&code_challenge=E9Melhoa2OwvFrEMTJguCHaoeK1t8URWbuGJSstw-cM\
	&code_challenge_method=S256\	&code_challenge_method=S256\
	&dpop_jkt=NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs HTTP/1.1	&dpop_jkt=NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs HTTP/1.1
	Host: server.example.com	Host: server.example.com
	</artwork>	]]></sourcecode>
	</figure>	</figure>

	<t>Use of the <tt>dpop_jkt</tt> authorization request parameter is OPTIONAL.	<t>Use of the <tt>dpop_jkt</tt> authorization request parameter is <bcp14>OPTION
	Note that the <tt>dpop_jkt</tt> authorization request parameter MAY also be used	AL</bcp14>.
	in combination with PKCE <xref target="RFC7636"></xref>, which is recommended by	Note that the <tt>dpop_jkt</tt> authorization request parameter <bcp14>MAY</bcp1
	<xref target="I-D.ietf-oauth-security-topics"></xref>	4> also be used
		in combination with Proof Key for Code Exchange (PKCE) <xref target="RFC7636"></
		xref>, which is recommended by <xref target="I-D.ietf-oauth-security-topics"></x
		ref>
	as a countermeasure to authorization code injection. The <tt>dpop_jkt</tt> autho rization	as a countermeasure to authorization code injection. The <tt>dpop_jkt</tt> autho rization
	request parameter only provides similar protections when a unique DPoP key is	request parameter only provides similar protections when a unique DPoP key is
	used for each authorization request.</t>	used for each authorization request.</t>

	<section anchor="dpop-with-pushed-authorization-requests"><name>DPoP with Pushed Authorization Requests</name>	<section anchor="dpop-with-pushed-authorization-requests"><name>DPoP with Pushed Authorization Requests</name>

	<t>When Pushed Authorization Requests (PAR, <xref target="RFC9126"></xref>) are used in conjunction with DPoP, there are two ways in which the DPoP key can be communicated in the PAR request:</t>	<t>When Pushed Authorization Requests (PARs) <xref target="RFC9126"></xref> are used in conjunction with DPoP, there are two ways in which the DPoP key can be c ommunicated in the PAR request:</t>

	<ul spacing="compact">	<ul spacing="compact">
	<li>The <tt>dpop_jkt</tt> parameter can be used as described in <xref target="dp op_jkt"></xref> to bind the issued	<li>The <tt>dpop_jkt</tt> parameter can be used as described in <xref target="dp op_jkt"></xref> to bind the issued

	authorization code to a specific key. In this case, <tt>dpop_jkt</tt> MUST be in cluded alongside other authorization request parameters in the POST body of the PAR request.</li>	authorization code to a specific key. In this case, <tt>dpop_jkt</tt> <bcp14>MUS T</bcp14> be included alongside other authorization request parameters in the PO ST body of the PAR request.</li>
	<li>Alternatively, the <tt>DPoP</tt> header can be added to the PAR request. In this	<li>Alternatively, the <tt>DPoP</tt> header can be added to the PAR request. In this

	case, the authorization server MUST check the provided DPoP proof JWT as	case, the authorization server <bcp14>MUST</bcp14> check the provided DPoP proof
	defined in <xref target="checking"></xref>. It MUST further behave as if the con	JWT as
	tained public key's	defined in <xref target="checking"></xref>. It <bcp14>MUST</bcp14> further behav
		e as if the contained public key's
	thumbprint was provided using <tt>dpop_jkt</tt>, i.e., reject the subsequent tok en	thumbprint was provided using <tt>dpop_jkt</tt>, i.e., reject the subsequent tok en
	request unless a DPoP proof for the same key is provided. This can help to	request unless a DPoP proof for the same key is provided. This can help to

	simplify the implementation of the client, as it can "blindly" attach the	simplify the implementation of the client, as it can "blindly" attach the
	<tt>DPoP</tt> header to all requests to the authorization server regardless of t he	<tt>DPoP</tt> header to all requests to the authorization server regardless of t he
	type of request. Additionally, it provides a stronger binding, as the <tt>DPoP</ tt>	type of request. Additionally, it provides a stronger binding, as the <tt>DPoP</ tt>
	header contains a proof of possession of the private key.</li>	header contains a proof of possession of the private key.</li>
	</ul>	</ul>

	<t>Both mechanisms MUST be supported by an authorization server that supports PA	<t>Both mechanisms <bcp14>MUST</bcp14> be supported by an authorization server t
	R and DPoP. If both mechanisms are used at the same time, the authorization serv	hat supports PAR and DPoP. If both mechanisms are used at the same time, the aut
	er MUST reject the request if the JWK Thumbprint in <tt>dpop_jkt</tt> does not m	horization server <bcp14>MUST</bcp14> reject the request if the JWK Thumbprint i
	atch the public key in the <tt>DPoP</tt> header.</t>	n <tt>dpop_jkt</tt> does not match the public key in the <tt>DPoP</tt> header.</
	<t>Allowing both mechanisms ensures that clients that use <tt>dpop_jkt</tt> do n	t>
	ot need to	<t>Allowing both mechanisms ensures that clients using <tt>dpop_jkt</tt> do not
		need to
	distinguish between front-channel and pushed authorization requests, and at the	distinguish between front-channel and pushed authorization requests, and at the
	same time, clients that only have one code path for protecting all calls to auth orization server	same time, clients that only have one code path for protecting all calls to auth orization server

	endpoints do not need to distinguish between requests to the PAR endpoint and	endpoints do not need to distinguish between requests to the PAR endpoint and th
	the token endpoint.</t>	e
		token endpoint.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="Security"><name>Security Considerations</name>	<section anchor="Security"><name>Security Considerations</name>
	<t>In DPoP, the prevention of token replay at a different endpoint (see	<t>In DPoP, the prevention of token replay at a different endpoint (see
	<xref target="objective"></xref>) is achieved through authentication of the serv er per <xref target="RFC6125"></xref> and	<xref target="objective"></xref>) is achieved through authentication of the serv er per <xref target="RFC6125"></xref> and

	binding of the DPoP proof to a certain URI and HTTP method. DPoP, however,	the binding of the DPoP proof to a certain URI and HTTP method. However, DPoP
	has a somewhat different nature of protection than TLS-based	has a somewhat different nature of protection than TLS-based
	methods such as OAuth Mutual TLS <xref target="RFC8705"></xref> or OAuth Token	methods such as OAuth Mutual TLS <xref target="RFC8705"></xref> or OAuth Token

	Binding <xref target="I-D.ietf-oauth-token-binding"></xref> (see also <xref targ et="Token_Replay"></xref> and <xref target="request_integrity"></xref>).	Binding <xref target="I-D.ietf-oauth-token-binding"></xref> (see also Sections < xref target="Token_Replay" format="counter"/> and <xref target="request_integrit y" format="counter"/>).
	TLS-based mechanisms can leverage a tight integration	TLS-based mechanisms can leverage a tight integration
	between the TLS layer and the application layer to achieve strong	between the TLS layer and the application layer to achieve strong
	message integrity, authenticity,	message integrity, authenticity,
	and replay protection.</t>	and replay protection.</t>

	<section anchor="Token_Replay"><name>DPoP Proof Replay</name>	<section anchor="Token_Replay"><name>DPoP Proof Replay</name>
	<t>If an adversary is able to get hold of a DPoP proof JWT, the adversary	<t>If an adversary is able to get hold of a DPoP proof JWT, the adversary
	could replay that token at the same endpoint (the HTTP endpoint	could replay that token at the same endpoint (the HTTP endpoint
	and method are enforced via the respective claims in the JWTs). To	and method are enforced via the respective claims in the JWTs). To

	limit this, servers MUST only accept DPoP proofs for a limited time	limit this, servers <bcp14>MUST</bcp14> only accept DPoP proofs for a limited ti me
	after their creation (preferably only for a relatively brief period	after their creation (preferably only for a relatively brief period
	on the order of seconds or minutes).</t>	on the order of seconds or minutes).</t>

	<t>To prevent multiple uses of the same DPoP proof, servers can store, in	<t>In the context of the target URI, servers can store the <tt>jti</tt> value of
	the context of the target URI, the <tt>jti</tt> value of each DPoP proof for the	each DPoP proof for the time window in which the respective DPoP proof JWT
	time window in which the respective DPoP proof JWT would be accepted.	would be accepted to prevent multiple uses of the same DPoP proof.
	HTTP requests to the same URI for which the <tt>jti</tt> value has been seen bef ore	HTTP requests to the same URI for which the <tt>jti</tt> value has been seen bef ore

	would be declined. Such a single-use check,	would be declined. When strictly enforced, such a single-use check provides a ve
	when strictly enforced, provides a very strong protection against DPoP	ry strong protection against DPoP
	proof replay, but may not always be feasible in practice, e.g., when	proof replay, but it may not always be feasible in practice, e.g., when
	multiple servers behind a single endpoint have no shared state.</t>	multiple servers behind a single endpoint have no shared state.</t>
	<t>In order to guard against	<t>In order to guard against
	memory exhaustion attacks, a server that is tracking <tt>jti</tt> values should reject	memory exhaustion attacks, a server that is tracking <tt>jti</tt> values should reject
	DPoP proof JWTs with unnecessarily large <tt>jti</tt> values or store only a has h thereof.</t>	DPoP proof JWTs with unnecessarily large <tt>jti</tt> values or store only a has h thereof.</t>

	<t>Note: To accommodate for clock offsets, the server MAY accept DPoP	<t>Note: To accommodate for clock offsets, the server <bcp14>MAY</bcp14> accept DPoP
	proofs that carry an <tt>iat</tt> time in the reasonably near future (on the ord er of seconds or minutes).	proofs that carry an <tt>iat</tt> time in the reasonably near future (on the ord er of seconds or minutes).
	Because clock skews between servers	Because clock skews between servers

	and clients may be large, servers MAY limit DPoP proof lifetimes by using	and clients may be large, servers <bcp14>MAY</bcp14> limit DPoP proof lifetimes by using
	server-provided nonce values containing the time at the server rather than	server-provided nonce values containing the time at the server rather than
	comparing the client-supplied <tt>iat</tt> time to the time at the server. Nonc es	comparing the client-supplied <tt>iat</tt> time to the time at the server. Nonc es
	created in this way yield the same result even in the face of arbitrarily	created in this way yield the same result even in the face of arbitrarily
	large clock skews.</t>	large clock skews.</t>
	<t>Server-provided nonces are an effective means for further reducing the chance s for successful DPoP proof replay.	<t>Server-provided nonces are an effective means for further reducing the chance s for successful DPoP proof replay.
	Unlike cryptographic nonces, it is acceptable for clients to use the same	Unlike cryptographic nonces, it is acceptable for clients to use the same

	<tt>nonce</tt> multiple times, and for the server to accept the same nonce multi	<tt>nonce</tt> multiple times and for the server to accept the same nonce multip
	ple	le
	times. As long as the <tt>jti</tt> value is tracked and duplicates rejected for	times. As long as the <tt>jti</tt> value is tracked and duplicates are rejected
	the lifetime of the <tt>nonce</tt>, there	for the lifetime of the <tt>nonce</tt>, there
	is no additional risk of token replay.</t>	is no additional risk of token replay.</t>
	</section>	</section>


	<section anchor="Pre-Generation"><name>DPoP Proof Pre-Generation</name>	<section anchor="Pre-Generation"><name>DPoP Proof Pre-generation</name>
	<t>An attacker in control of the client can pre-generate DPoP proofs for	<t>An attacker in control of the client can pre-generate DPoP proofs for
	specific endpoints arbitrarily far into the future by choosing the	specific endpoints arbitrarily far into the future by choosing the
	<tt>iat</tt> value in the DPoP proof to be signed by the proof-of-possession key .	<tt>iat</tt> value in the DPoP proof to be signed by the proof-of-possession key .
	Note that one such attacker is the person who is the legitimate user of the clie nt.	Note that one such attacker is the person who is the legitimate user of the clie nt.
	The user may pre-generate DPoP proofs to exfiltrate	The user may pre-generate DPoP proofs to exfiltrate
	from the machine possessing the proof-of-possession key	from the machine possessing the proof-of-possession key
	upon which they were generated	upon which they were generated
	and copy them to another machine that does not possess the key.	and copy them to another machine that does not possess the key.
	For instance, a bank employee might pre-generate DPoP proofs	For instance, a bank employee might pre-generate DPoP proofs
	on a bank computer and then copy them to another machine	on a bank computer and then copy them to another machine

	skipping to change at line 1155 ¶	skipping to change at line 1178 ¶
	is possession of a DPoP proof -- not of the proof-of-possession key.</t>	is possession of a DPoP proof -- not of the proof-of-possession key.</t>
	<t>Use of server-provided nonce values that are not predictable by attackers can prevent this attack.	<t>Use of server-provided nonce values that are not predictable by attackers can prevent this attack.
	By providing new nonce values at times of its choosing,	By providing new nonce values at times of its choosing,
	the server can limit the lifetime of DPoP proofs,	the server can limit the lifetime of DPoP proofs,
	preventing pre-generated DPoP proofs from being used.	preventing pre-generated DPoP proofs from being used.
	When server-provided nonces are used, possession	When server-provided nonces are used, possession
	of the proof-of-possession key is being demonstrated --	of the proof-of-possession key is being demonstrated --
	not just possession of a DPoP proof.</t>	not just possession of a DPoP proof.</t>
	<t>The <tt>ath</tt> claim limits the use of pre-generated DPoP proofs to the lif etime	<t>The <tt>ath</tt> claim limits the use of pre-generated DPoP proofs to the lif etime
	of the access token. Deployments that do not utilize the nonce mechanism	of the access token. Deployments that do not utilize the nonce mechanism

	SHOULD NOT issue long-lived DPoP constrained access tokens,	<bcp14>SHOULD NOT</bcp14> issue long-lived DPoP constrained access tokens,
	preferring instead to use short-lived access tokens and refresh tokens.	preferring instead to use short-lived access tokens and refresh tokens.
	Whilst an attacker could pre-generate DPoP proofs to use the refresh token	Whilst an attacker could pre-generate DPoP proofs to use the refresh token
	to obtain a new access token, they would be unable to realistically	to obtain a new access token, they would be unable to realistically
	pre-generate DPoP proofs to use a newly issued access token.</t>	pre-generate DPoP proofs to use a newly issued access token.</t>
	</section>	</section>

	<section anchor="Nonce-Downgrade"><name>DPoP Nonce Downgrade</name>	<section anchor="Nonce-Downgrade"><name>DPoP Nonce Downgrade</name>

	<t>A server MUST NOT accept any DPoP proofs without the <tt>nonce</tt> claim whe n a DPoP nonce has been provided to the client.</t>	<t>A server <bcp14>MUST NOT</bcp14> accept any DPoP proofs without the <tt>nonce </tt> claim when a DPoP nonce has been provided to the client.</t>
	</section>	</section>

	<section anchor="untrusted-code-in-the-client-context"><name>Untrusted Code in t he Client Context</name>	<section anchor="untrusted-code-in-the-client-context"><name>Untrusted Code in t he Client Context</name>
	<t>If an adversary is able to run code in the client's execution context,	<t>If an adversary is able to run code in the client's execution context,
	the security of DPoP is no longer guaranteed. Common issues in web	the security of DPoP is no longer guaranteed. Common issues in web

	applications leading to the execution of untrusted code are cross-site	applications leading to the execution of untrusted code are XSS and remote code
	scripting and remote code inclusion attacks.</t>	inclusion attacks.</t>
	<t>If the private key used for DPoP is stored in such a way that it	<t>If the private key used for DPoP is stored in such a way that it
	cannot be exported, e.g., in a hardware or software security module,	cannot be exported, e.g., in a hardware or software security module,
	the adversary cannot exfiltrate the key and use it to create arbitrary	the adversary cannot exfiltrate the key and use it to create arbitrary
	DPoP proofs. The adversary can, however, create new DPoP proofs as	DPoP proofs. The adversary can, however, create new DPoP proofs as

	long as the client is online, and use these proofs (together with the	long as the client is online and uses these proofs (together with the
	respective tokens) either on the victim's device or on a device under	respective tokens) either on the victim's device or on a device under
	the attacker's control to send arbitrary requests that will be	the attacker's control to send arbitrary requests that will be
	accepted by servers.</t>	accepted by servers.</t>
	<t>To send requests even when the client is offline, an adversary can try	<t>To send requests even when the client is offline, an adversary can try
	to pre-compute DPoP proofs using timestamps in the future and	to pre-compute DPoP proofs using timestamps in the future and
	exfiltrate these together with the access or refresh token.</t>	exfiltrate these together with the access or refresh token.</t>
	<t>An adversary might further try to associate tokens issued from the	<t>An adversary might further try to associate tokens issued from the
	token endpoint with a key pair under the adversary's control. One way	token endpoint with a key pair under the adversary's control. One way
	to achieve this is to modify existing code, e.g., by replacing	to achieve this is to modify existing code, e.g., by replacing
	cryptographic APIs. Another way is to launch a new authorization grant	cryptographic APIs. Another way is to launch a new authorization grant
	between the client and the authorization server in an iframe. This	between the client and the authorization server in an iframe. This

	grant needs to be "silent", i.e., not require interaction with the	grant needs to be "silent", i.e., not require interaction with the
	user. With code running in the client's origin, the adversary has	user. With code running in the client's origin, the adversary has
	access to the resulting authorization code and can use it to associate	access to the resulting authorization code and can use it to associate
	their own DPoP keys with the tokens returned from the token endpoint.	their own DPoP keys with the tokens returned from the token endpoint.
	The adversary is then able to use the resulting tokens on their own	The adversary is then able to use the resulting tokens on their own
	device even if the client is offline.</t>	device even if the client is offline.</t>
	<t>Therefore, protecting clients against the execution of untrusted code	<t>Therefore, protecting clients against the execution of untrusted code
	is extremely important even if DPoP is used. Besides secure coding	is extremely important even if DPoP is used. Besides secure coding
	practices, Content Security Policy <xref target="W3C.CSP"></xref> can be used as a second	practices, Content Security Policy <xref target="W3C.CSP"></xref> can be used as a second

	layer of defense against cross-site scripting.</t>	layer of defense against XSS.</t>
	</section>	</section>

	<section anchor="signed-jwt-swapping"><name>Signed JWT Swapping</name>	<section anchor="signed-jwt-swapping"><name>Signed JWT Swapping</name>

	<t>Servers accepting signed DPoP proof JWTs MUST verify that the <tt>typ</tt> fi eld is <tt>dpop+jwt</tt> in the	<t>Servers accepting signed DPoP proof JWTs <bcp14>MUST</bcp14> verify that the <tt>typ</tt> field is <tt>dpop+jwt</tt> in the
	headers of the JWTs to ensure that adversaries cannot use JWTs created	headers of the JWTs to ensure that adversaries cannot use JWTs created
	for other purposes.</t>	for other purposes.</t>
	</section>	</section>

	<section anchor="signature-algorithms"><name>Signature Algorithms</name>	<section anchor="signature-algorithms"><name>Signature Algorithms</name>

	<t>Implementers MUST ensure that only asymmetric digital signature algorithms (s uch as <tt>ES256</tt>) that	<t>Implementers <bcp14>MUST</bcp14> ensure that only asymmetric digital signatur e algorithms (such as <tt>ES256</tt>) that
	are deemed secure can be used for signing DPoP proofs. In particular,	are deemed secure can be used for signing DPoP proofs. In particular,

	the algorithm <tt>none</tt> MUST NOT be allowed.</t>	the algorithm <tt>none</tt> <bcp14>MUST NOT</bcp14> be allowed.</t>
	</section>	</section>

	<section anchor="request_integrity"><name>Request Integrity</name>	<section anchor="request_integrity"><name>Request Integrity</name>
	<t>DPoP does not ensure the integrity of the payload or headers of	<t>DPoP does not ensure the integrity of the payload or headers of
	requests. The DPoP proof only contains claims for the HTTP URI and	requests. The DPoP proof only contains claims for the HTTP URI and

	method, but not, for example, the message body or general request	method, but not the message body or general request
	headers.</t>	headers, for example.</t>
	<t>This is an intentional design decision intended to keep DPoP simple to use, b ut	<t>This is an intentional design decision intended to keep DPoP simple to use, b ut

	as described, makes DPoP potentially susceptible to replay attacks	as described, it makes DPoP potentially susceptible to replay attacks
	where an attacker is able to modify message contents and headers. In	where an attacker is able to modify message contents and headers. In
	many setups, the message integrity and confidentiality provided by TLS	many setups, the message integrity and confidentiality provided by TLS
	is sufficient to provide a good level of protection.</t>	is sufficient to provide a good level of protection.</t>
	<t>Note: While signatures covering other parts of requests are out of the scope of	<t>Note: While signatures covering other parts of requests are out of the scope of
	this specification, additional information to be signed can be	this specification, additional information to be signed can be
	added into DPoP proofs.</t>	added into DPoP proofs.</t>
	</section>	</section>

	<section anchor="access-token-and-public-key-binding"><name>Access Token and Pub lic Key Binding</name>	<section anchor="access-token-and-public-key-binding"><name>Access Token and Pub lic Key Binding</name>

	<t>The binding of the access token to the DPoP public key, which is	<t>The binding of the access token to the DPoP public key, as specified in <xref
	specified in <xref target="Confirmation"></xref>, uses a cryptographic hash of t	target="Confirmation"></xref>, uses a cryptographic hash of the JWK
	he JWK
	representation of the public key. It relies	representation of the public key. It relies
	on the hash function having sufficient second-preimage resistance so	on the hash function having sufficient second-preimage resistance so
	as to make it computationally infeasible to find or create another	as to make it computationally infeasible to find or create another
	key that produces to the same hash output value. The SHA-256	key that produces to the same hash output value. The SHA-256
	hash function was used because it meets the aforementioned	hash function was used because it meets the aforementioned
	requirement while being widely available.</t>	requirement while being widely available.</t>
	<t>Similarly, the binding of the DPoP proof to the access token uses a	<t>Similarly, the binding of the DPoP proof to the access token uses a
	hash of that access token as the value of the <tt>ath</tt> claim	hash of that access token as the value of the <tt>ath</tt> claim
	in the DPoP proof (see <xref target="DPoP-Proof-Syntax"></xref>). This relies on the value	in the DPoP proof (see <xref target="DPoP-Proof-Syntax"></xref>). This relies on the value
	of the hash being sufficiently unique so as to reliably identify the	of the hash being sufficiently unique so as to reliably identify the
	access token. The collision resistance of SHA-256 meets that requirement.</t>	access token. The collision resistance of SHA-256 meets that requirement.</t>
	</section>	</section>

	<section anchor="authorization-code-and-public-key-binding"><name>Authorization Code and Public Key Binding</name>	<section anchor="authorization-code-and-public-key-binding"><name>Authorization Code and Public Key Binding</name>

	<t>Cryptographic binding of the authorization code to the DPoP public key,	<t>Cryptographic binding of the authorization code to the DPoP public key
	is specified in <xref target="dpop_jkt"></xref>.	is specified in <xref target="dpop_jkt"></xref>.

	This binding prevents attacks in which the attacker captures the authorization c	This binding prevents attacks in which the attacker captures the
	ode	authorization code and creates a DPoP proof using a proof-of-possession key
	and creates a DPoP proof using a proof-of-possession key	other than the one held by the client and redeems the authorization code
	other than that held by the client	using that DPoP proof. By ensuring end to end that only the client's DPoP
	and redeems the authorization code using that DPoP proof.	key can be used, this prevents captured authorization codes from being
	By ensuring end-to-end that only the client's DPoP key can be used,	exfiltrated and used at locations other than the one to which the
	this prevents captured authorization codes from being exfiltrated and used	authorization code was issued.</t>
	at locations other than the one to which the authorization code was issued.</t>
	<t>Authorization codes can, for instance, be harvested by attackers	<t>Authorization codes can, for instance, be harvested by attackers

	from places that the HTTP messages containing them are logged.	from places where the HTTP messages containing them are logged.
	Even when efforts are made to make authorization codes one-time-use,	Even when efforts are made to make authorization codes one-time-use, in practice
	in practice, there is often a time window during which attackers can replay them	,
	.	there is often a time window during which attackers can replay them.
	For instance, when authorization servers are implemented as scalable replicated services,	For instance, when authorization servers are implemented as scalable replicated services,
	some replicas may temporarily not yet have the information needed to prevent rep lay.	some replicas may temporarily not yet have the information needed to prevent rep lay.
	DPoP binding of the authorization code solves these problems.</t>	DPoP binding of the authorization code solves these problems.</t>
	<t>If an authorization server does not (or cannot) strictly enforce the single-u se limitation for authorization codes	<t>If an authorization server does not (or cannot) strictly enforce the single-u se limitation for authorization codes
	and an attacker can access the authorization code (and if PKCE is used, the <tt> code_verifier</tt>),	and an attacker can access the authorization code (and if PKCE is used, the <tt> code_verifier</tt>),
	the attacker can create a forged token request, binding the resulting token to a n attacker-controlled key.	the attacker can create a forged token request, binding the resulting token to a n attacker-controlled key.

	For example, using cross-site scripting, attackers might obtain access to the au thorization code and PKCE parameters.	For example, using XSS, attackers might obtain access to the authorization code and PKCE parameters.
	Use of the <tt>dpop_jkt</tt> parameter prevents this attack.</t>	Use of the <tt>dpop_jkt</tt> parameter prevents this attack.</t>
	<t>The binding of the authorization code to the DPoP public key	<t>The binding of the authorization code to the DPoP public key
	uses a JWK Thumbprint of the public key, just as the access token binding does.	uses a JWK Thumbprint of the public key, just as the access token binding does.
	The same JWK Thumbprint considerations apply.</t>	The same JWK Thumbprint considerations apply.</t>
	</section>	</section>

	<section anchor="hash-algorithm-agility"><name>Hash Algorithm Agility</name>	<section anchor="hash-algorithm-agility"><name>Hash Algorithm Agility</name>
	<t>The <tt>jkt</tt> confirmation method member, the <tt>ath</tt> JWT claim, and the <tt>dpop_jkt</tt> authorization	<t>The <tt>jkt</tt> confirmation method member, the <tt>ath</tt> JWT claim, and the <tt>dpop_jkt</tt> authorization
	request parameter defined herein all use the output of the SHA-256 hash function as their value.	request parameter defined herein all use the output of the SHA-256 hash function as their value.
	The use of a single hash function by this specification was intentional and aime d at	The use of a single hash function by this specification was intentional and aime d at
	simplicity and avoidance of potential security and interoperability issues arisi ng from	simplicity and avoidance of potential security and interoperability issues arisi ng from
	common mistakes implementing and deploying parameterized algorithm agility schem es.	common mistakes implementing and deploying parameterized algorithm agility schem es.

	The use of a different hash function is not precluded, however, if future circum	However, the use of a different hash function is not precluded if future circums
	stances	tances
	change making SHA-256 insufficient for the requirements of this specification.	change and make SHA-256 insufficient for the requirements of this specification.
	Should that need arise, it is expected that a short specification be produced th	Should that need arise, it is expected that a short specification will be produc
	at	ed that
	updates this one. That specification will likely define, using the output of a t	updates this one.
	hen appropriate	Using the output of an appropriate
	hash function as the value, a new confirmation method member, a new JWT claim,	hash function as the value, that specification will likely define a new confirma
		tion method member, a new JWT claim,
	and a new authorization request parameter. These items will be used in place of, or alongside, their	and a new authorization request parameter. These items will be used in place of, or alongside, their
	respective counterparts in the same message structures and flows of the larger p rotocol defined	respective counterparts in the same message structures and flows of the larger p rotocol defined
	by this specification.</t>	by this specification.</t>
	</section>	</section>

	<section anchor="binding-to-client-identity"><name>Binding to Client Identity</n ame>	<section anchor="binding-to-client-identity"><name>Binding to Client Identity</n ame>
	<t>In cases where DPoP is used with client authentication, it is only bound to a uthentication by being	<t>In cases where DPoP is used with client authentication, it is only bound to a uthentication by being

	coincident in the same TLS tunnel. Since the DPoP proof is not directly cryptog	coincident in the same TLS tunnel. Since the DPoP proof is not directly bound
	raphically bound	to the authentication cryptographically, it's possible that the authentication o
	to the authentication, it's possible that the authentication or the DPoP message	r the DPoP messages were copied into
	s were copied into
	the tunnel. While including the URI in the DPoP can partially mitigate some of this risk, modifying	the tunnel. While including the URI in the DPoP can partially mitigate some of this risk, modifying
	the authentication mechanism to provide cryptographic binding between authentica tion and DPoP could	the authentication mechanism to provide cryptographic binding between authentica tion and DPoP could
	provide better protection. However, providing additional binding with authentic ation through the	provide better protection. However, providing additional binding with authentic ation through the
	modification of authentication mechanisms or other means is beyond the scope of this specification.</t>	modification of authentication mechanisms or other means is beyond the scope of this specification.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="IANA"><name>IANA Considerations</name>	<section anchor="IANA"><name>IANA Considerations</name>

		<section anchor="oauth-access-token-type-registration"><name>OAuth Access Token
	<section anchor="oauth-access-token-type-registration"><name>OAuth Access Token	Types Registration</name>
	Type Registration</name>	<t>IANA has registered the following access token
	<t>This specification requests registration of the following access token	type in the "OAuth Access Token Types" registry <xref target="IANA.OAuth.Params"
	type in the "OAuth Access Token Types" registry <xref target="IANA.OAu	></xref>
	th.Params"></xref>
	established by <xref target="RFC6749"></xref>.</t>	established by <xref target="RFC6749"></xref>.</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Type name: <tt>DPoP</tt></li>	<dt>Name:</dt><dd><tt>DPoP</tt></dd>
	<li>Additional Token Endpoint Response Parameters: (none)</li>	<dt>Additional Token Endpoint Response Parameters:</dt><dd>(none)</dd>
	<li>HTTP Authentication Scheme(s): <tt>DPoP</tt></li>	<dt>HTTP Authentication Scheme(s):</dt><dd><tt>DPoP</tt></dd>
	<li>Change controller: IETF</li>	<dt>Change Controller:</dt><dd>IETF</dd>
	<li>Specification document(s): [[ this specification ]]</li>	<dt>Reference:</dt><dd>RFC 9449</dd>
	</ul>	</dl>
	</section>	</section>

	<section anchor="oauth-extensions-error-registration"><name>OAuth Extensions Err or Registration</name>	<section anchor="oauth-extensions-error-registration"><name>OAuth Extensions Err or Registration</name>

	<t>This specification requests registration of the following error values	<t>IANA has registered the following error values
	in the "OAuth Extensions Error" registry <xref target="IANA.OAuth.Para	in the "OAuth Extensions Error" registry <xref target="IANA.OAuth.Params"></xref
	ms"></xref>	>
	established by <xref target="RFC6749"></xref>.</t>	established by <xref target="RFC6749"></xref>.</t>

	<t>Invalid DPoP proof:</t>	<dl spacing="normal">
		<dt>Invalid DPoP proof:</dt>
	<ul spacing="compact">	<dd><t><br/></t>
	<li>Name: <tt>invalid_dpop_proof</tt></li>	<dl spacing="normal">
	<li>Usage Location: token error response, resource access error response</li>	<dt>Name:</dt><dd><tt>invalid_dpop_proof</tt></dd>
	<li>Protocol Extension: Demonstrating Proof of Possession (DPoP)</li>	<dt>Usage Location:</dt><dd>token error response, resource access error response
	<li>Change controller: IETF</li>	</dd>
	<li>Specification document(s): [[ this specification ]]</li>	<dt>Protocol Extension:</dt><dd>Demonstrating Proof of Possession (DPoP)</dd>
	</ul>	<dt>Change Controller:</dt><dd>IETF</dd>
	<t>Use DPoP nonce:</t>	<dt>Reference:</dt><dd>RFC 9449</dd>
		</dl>
		</dd>
		</dl>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Name: <tt>use_dpop_nonce</tt></li>	<dt>Use DPoP nonce:</dt>
	<li>Usage Location: token error response, resource access error response</li>	<dd>
	<li>Protocol Extension: Demonstrating Proof of Possession (DPoP)</li>	<t><br/></t>
	<li>Change controller: IETF</li>	<dl spacing="normal">
	<li>Specification document(s): [[ this specification ]]</li>	<dt>Name:</dt><dd><tt>use_dpop_nonce</tt></dd>
	</ul>	<dt>Usage Location:</dt><dd>token error response, resource access error response
		</dd>
		<dt>Protocol Extension:</dt><dd>Demonstrating Proof of Possession (DPoP)</dd>
		<dt>Change Controller:</dt><dd>IETF</dd>
		<dt>Reference:</dt><dd>RFC 9449</dd>
		</dl></dd></dl>
	</section>	</section>

	<section anchor="oauth-parameters-registration"><name>OAuth Parameters Registrat ion</name>	<section anchor="oauth-parameters-registration"><name>OAuth Parameters Registrat ion</name>

	<t>This specification requests registration of the following	<t>IANA has registered the following authorization request parameter
	authorization request parameter	in the "OAuth Parameters" registry <xref target="IANA.OAuth.Params"></xref>
	in the "OAuth Parameters" registry <xref target="IANA.OAuth.Params"></
	xref>
	established by <xref target="RFC6749"></xref>.</t>	established by <xref target="RFC6749"></xref>.</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Name: <tt>dpop_jkt</tt></li>	<dt>Name:</dt><dd><tt>dpop_jkt</tt></dd>
	<li>Parameter Usage Location: authorization request</li>	<dt>Parameter Usage Location:</dt><dd>authorization request</dd>
	<li>Change Controller: IETF</li>	<dt>Change Controller:</dt><dd>IETF</dd>
	<li>Reference: [[ <xref target="dpop_jkt"></xref> of this specification ]]</li>	<dt>Reference:</dt><dd><xref target="dpop_jkt"></xref> of RFC 9449</dd>
	</ul>	</dl>
	</section>	</section>


	<section anchor="http-authentication-scheme-registration"><name>HTTP Authenticat	<section anchor="http-authentication-scheme-registration"><name>HTTP Authenticat
	ion Scheme Registration</name>	ion Schemes Registration</name>
	<t>This specification requests registration of the following scheme in the	<t>IANA has registered the following scheme in the
	"Hypertext Transfer Protocol (HTTP) Authentication Scheme Registry" <x	"HTTP Authentication Schemes" registry <xref target="IANA.HTTP.AuthSchemes"></xr
	ref target="RFC9110"></xref><xref target="IANA.HTTP.AuthSchemes"></xref>:</t>	ef> established by <xref target="RFC9110" sectionFormat="comma" section="16.4.1"
		></xref>.</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Authentication Scheme Name: <tt>DPoP</tt></li>	<dt>Authentication Scheme Name:</dt><dd><tt>DPoP</tt></dd>
	<li>Reference: [[ <xref target="http-auth-scheme"></xref> of this specification	<dt>Reference:</dt><dd><xref target="http-auth-scheme"></xref> of RFC 9449</dd>
	]]</li>	</dl>
	</ul>
	</section>	</section>

	<section anchor="media-type-registration"><name>Media Type Registration</name>	<section anchor="media-type-registration"><name>Media Type Registration</name>

	<t>This section registers the <tt>application/dpop+jwt</tt> media type <xref tar	<t>IANA has registered the <tt>application/dpop+jwt</tt> media type <xref target
	get="RFC2046"></xref>	="RFC2046"></xref>
	in the IANA "Media Types" registry <xref target="IANA.MediaTypes"></xr	in the "Media Types" registry <xref target="IANA.MediaTypes"></xref> in the mann
	ef> in the manner described in <xref target="RFC6838"></xref>,	er described in <xref target="RFC6838"></xref>,
	which is used to indicate that the content is a DPoP JWT.</t>	which is used to indicate that the content is a DPoP JWT.</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Type name: application</li>	<dt>Type name:</dt><dd>application</dd>
	<li>Subtype name: dpop+jwt</li>	<dt>Subtype name:</dt><dd>dpop+jwt</dd>
	<li>Required parameters: n/a</li>	<dt>Required parameters:</dt><dd>n/a</dd>
	<li>Optional parameters: n/a</li>	<dt>Optional parameters:</dt><dd> n/a</dd>
	<li>Encoding considerations: binary; A DPoP JWT is a JWT; JWT values are encoded	<dt>Encoding considerations:</dt><dd>binary. A DPoP JWT is a JWT; JWT values are
	as a series of base64url-encoded values (some of which may be the empty string)	encoded as a series of base64url-encoded values (some of which may be the empty
	separated by period ('.') characters.</li>	string) separated by period ('.') characters.</dd>
	<li>Security considerations: See <xref target="Security"></xref> of [[ this spec	<dt>Security considerations:</dt><dd>See <xref target="Security"></xref> of RFC
	ification ]]</li>	9449</dd>
	<li>Interoperability considerations: n/a</li>	<dt>Interoperability considerations:</dt><dd>n/a</dd>
	<li>Published specification: [[ this specification ]]</li>	<dt>Published specification:</dt><dd>RFC 9449</dd>
	<li>Applications that use this media type: Applications using [[ this specificat	<dt>Applications that use this media type:</dt><dd>Applications using RFC 9449 f
	ion ]] for application-level proof of possession</li>	or application-level proof of possession</dd>
	<li>Fragment identifier considerations: n/a</li>	<dt>Fragment identifier considerations:</dt><dd>n/a</dd>
	<li><t>Additional information:</t>	<dt>Additional information:</dt>
		<dd>
	<ul spacing="compact">	<t><br/></t>
	<li>File extension(s): n/a</li>	<dl spacing="compact">
	<li>Macintosh file type code(s): n/a</li>	<dt>File extension(s):</dt><dd>n/a</dd>
	</ul></li>	<dt>Macintosh file type code(s):</dt><dd>n/a</dd>
	<li>Person & email address to contact for further information: Michael B. Jo	</dl></dd>
	nes, mbj@microsoft.com</li>	<dt>Person & email address to contact for further information:</dt><dd>Micha
	<li>Intended usage: COMMON</li>	el B. Jones, michael_b_jones@hotmail.com</dd>
	<li>Restrictions on usage: none</li>	<dt>Intended usage:</dt><dd>COMMON</dd>
	<li>Author: Michael B. Jones, mbj@microsoft.com</li>	<dt>Restrictions on usage:</dt><dd>none</dd>
	<li>Change controller: IETF</li>	<dt>Author:</dt><dd>Michael B. Jones, michael_b_jones@hotmail.com</dd>
	<li>Provisional registration? No</li>	<dt>Change controller:</dt><dd>IETF</dd>
	</ul>	</dl>
	</section>	</section>

	<section anchor="jwt-confirmation-methods-registration"><name>JWT Confirmation M ethods Registration</name>	<section anchor="jwt-confirmation-methods-registration"><name>JWT Confirmation M ethods Registration</name>

	<t>This specification requests registration of the following value	<t>IANA has registered the following JWT <tt>cnf</tt> member value
	in the IANA "JWT Confirmation Methods" registry <xref target="IANA.JWT	in the "JWT Confirmation Methods" registry <xref target="IANA.JWT"></xref>
	"></xref>	established by <xref target="RFC7800"></xref>.</t>
	for JWT <tt>cnf</tt> member values established by <xref target="RFC7800"></xref>
	.</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Confirmation Method Value: <tt>jkt</tt></li>	<dt>Confirmation Method Value:</dt><dd><tt>jkt</tt></dd>
	<li>Confirmation Method Description: JWK SHA-256 Thumbprint</li>	<dt>Confirmation Method Description:</dt><dd>JWK SHA-256 Thumbprint</dd>
	<li>Change Controller: IETF</li>	<dt>Change Controller:</dt><dd>IETF</dd>
	<li>Specification Document(s): [[ <xref target="Confirmation"></xref> of this s	<dt>Reference:</dt><dd><xref target="Confirmation"></xref> of RFC 9449</dd>
	pecification ]]</li>	</dl>
	</ul>
	</section>	</section>

	<section anchor="json-web-token-claims-registration"><name>JSON Web Token Claims Registration</name>	<section anchor="json-web-token-claims-registration"><name>JSON Web Token Claims Registration</name>

	<t>This specification requests registration of the following Claims in the	<t>IANA has registered the following Claims in the "JSON Web Token Claims" regis
	IANA "JSON Web Token Claims" registry <xref target="IANA.JWT"></xref>	try <xref target="IANA.JWT"></xref> established by <xref target="RFC7519"></xref
	established by <xref target="RFC7519"></xref>.</t>	>.</t>
	<t>HTTP method:</t>	<dl spacing="normal">
		<dt>HTTP method:</dt>
	<ul spacing="compact">	<dd>
	<li>Claim Name: <tt>htm</tt></li>	<t><br/></t>
	<li>Claim Description: The HTTP method of the request</li>	<dl spacing="normal">
	<li>Change Controller: IETF</li>	<dt>Claim Name:</dt><dd><tt>htm</tt></dd>
	<li>Specification Document(s): [[ <xref target="DPoP-Proof-Syntax"></xref> of t	<dt>Claim Description:</dt><dd>The HTTP method of the request</dd>
	his specification ]]</li>	<dt>Change Controller:</dt><dd>IETF</dd>
	</ul>	<dt>Reference:</dt><dd><xref target="DPoP-Proof-Syntax"></xref> of RFC 9449</dd>
	<t>HTTP URI:</t>	</dl>
		</dd></dl>
	<ul spacing="compact">	<dl spacing="normal">
	<li>Claim Name: <tt>htu</tt></li>	<dt>HTTP URI:</dt>
	<li>Claim Description: The HTTP URI of the request (without query and fragment p	<dd>
	arts)</li>	<t><br/></t>
	<li>Change Controller: IETF</li>	<dl spacing="normal">
	<li>Specification Document(s): [[ <xref target="DPoP-Proof-Syntax"></xref> of t	<dt>Claim Name:</dt><dd><tt>htu</tt></dd>
	his specification ]]</li>	<dt>Claim Description:</dt><dd>The HTTP URI of the request (without query and fr
	</ul>	agment parts)</dd>
	<t>Access token hash:</t>	<dt>Change Controller:</dt><dd>IETF</dd>
		<dt>Reference:</dt><dd><xref target="DPoP-Proof-Syntax"></xref> of RFC 9449</dd>
	<ul spacing="compact">	</dl></dd></dl>
	<li>Claim Name: <tt>ath</tt></li>	<dl spacing="normal">
	<li>Claim Description: The base64url encoded SHA-256 hash of the ASCII encoding	<dt>Access token hash:</dt>
	of the associated access token's value</li>	<dd>
	<li>Change Controller: IETF</li>	<t><br/></t>
	<li>Specification Document(s): [[ <xref target="DPoP-Proof-Syntax"></xref> of t	<dl spacing="normal">
	his specification ]]</li>	<dt>Claim Name:</dt><dd><tt>ath</tt></dd>
	</ul>	<dt>Claim Description:</dt><dd>The base64url-encoded SHA-256 hash of the ASCII e
		ncoding of the associated access token's value</dd>
	<section anchor="nonce-registry-update"><name>"nonce" Registry Update<	<dt>Change Controller:</dt><dd>IETF</dd>
	/name>	<dt>Reference:</dt><dd><xref target="DPoP-Proof-Syntax"></xref> of RFC 9449</dd>
		</dl>
		</dd>
		</dl>
		<section anchor="nonce-registry-update"><name>"nonce" Registration Update</name>
	<t>The Internet Security Glossary <xref target="RFC4949"></xref> provides a usef ul definition of nonce	<t>The Internet Security Glossary <xref target="RFC4949"></xref> provides a usef ul definition of nonce
	as a random or non-repeating value that is included in data	as a random or non-repeating value that is included in data
	exchanged by a protocol, usually for the purpose of guaranteeing	exchanged by a protocol, usually for the purpose of guaranteeing
	liveness and thus detecting and protecting against replay attacks.</t>	liveness and thus detecting and protecting against replay attacks.</t>
	<t>However, the initial registration of the <tt>nonce</tt> claim by <xref target ="OpenID.Core"></xref>	<t>However, the initial registration of the <tt>nonce</tt> claim by <xref target ="OpenID.Core"></xref>
	used language that was contextually specific to that application,	used language that was contextually specific to that application,
	which was potentially limiting to its general applicability.</t>	which was potentially limiting to its general applicability.</t>

	<t>This specification therefore requests that the entry for <tt>nonce</tt> in th	<t>Therefore, IANA has updated the entry for <tt>nonce</tt> in the
	e	"JSON Web Token Claims" registry <xref target="IANA.JWT"></xref> with an expande
	IANA "JSON Web Token Claims" registry <xref target="IANA.JWT"></xref>	d definition to reflect
	be updated as follows to	that the claim can be used appropriately in other contexts and with the addition
	reflect that the claim can be used appropriately in other contexts.</t>	of this document as a reference, as follows.</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Claim Name: <tt>nonce</tt></li>	<dt>Claim Name:</dt><dd><tt>nonce</tt></dd>
	<li>Claim Description: Value used to associate a Client session with an ID Token	<dt>Claim Description:</dt><dd>Value used to associate a Client session with an
	(MAY also be used for nonce values in other applications of JWTs)</li>	ID Token (<bcp14>MAY</bcp14> also be used for nonce values in other applications
	<li>Change Controller: OpenID Foundation Artifact Binding Working Group - openid	of JWTs)</dd>
	-specs-ab@lists.openid.net</li>	<dt>Change Controller:</dt><dd>OpenID Foundation Artifact Binding Working Group,
	<li>Specification Document(s): <xref target="OpenID.Core" sectionFormat="of" re	openid-specs-ab@lists.openid.net</dd>
	lative="#" section="2"></xref> and [[ this specification ]]</li>	<dt>Specification Document(s):</dt><dd><xref target="OpenID.Core" sectionFormat=
	</ul>	"of" relative="openid-connect-core-1_0.html#IDToken" section="2"></xref> and RFC
		9449</dd>
		</dl>
	</section>	</section>
	</section>	</section>


	<section anchor="http-message-header-field-names-registration"><name>HTTP Messag	<section anchor="http-message-header-field-names-registration"><name>Hypertext T
	e Header Field Names Registration</name>	ransfer Protocol (HTTP) Field Name Registration</name>
	<t>This document specifies the following HTTP header fields,	<t>IANA has registered the following HTTP header fields, as specified by this do
	registration of which is requested in the "Hypertext Transfer Protocol (HTT	cument, in the "Hypertext Transfer Protocol (HTTP) Field Name Registry"
	P) Field Name Registry"	<xref target="IANA.HTTP.Fields"></xref> established by <xref target="RFC9110"><
	registry <xref target="RFC9110"></xref><xref target="IANA.HTTP.Fields"></xref>:<	/xref>:</t>
	/t>


	<ul>	<dl spacing="normal">
	<li>Field name: <tt>DPoP</tt></li>	<dt>DPoP:</dt>
	<li>Status: permanent</li>	<dd>
	<li><t>Specification document: [[ this specification ]]	<t><br/></t>
	<br />	<dl spacing="normal">
	</t>	<dt>Field Name:</dt><dd><tt>DPoP</tt></dd>
	</li>	<dt>Status:</dt><dd>permanent</dd>
	<li><t>Field name: <tt>DPoP-Nonce</tt></t>	<dt>Reference:</dt><dd>RFC 9449</dd>
	</li>	</dl>
	<li><t>Status: permanent</t>	</dd>
	</li>	</dl>
	<li><t>Specification document: [[ this specification ]]</t>	<dl spacing="normal">
	</li>	<dt>DPoP-Nonce:</dt>
	</ul>	<dd>
		<t><br/></t>
		<dl spacing="normal">
		<dt>Field Name:</dt><dd><tt>DPoP-Nonce</tt></dd>
		<dt>Status:</dt><dd>permanent</dd>
		<dt>Reference:</dt><dd>RFC 9449</dd>
		</dl>
		</dd>
		</dl>
	</section>	</section>

	<section anchor="oauth-authorization-server-metadata-registration"><name>OAuth A uthorization Server Metadata Registration</name>	<section anchor="oauth-authorization-server-metadata-registration"><name>OAuth A uthorization Server Metadata Registration</name>

	<t>This specification requests registration of the following value	<t>IANA has registered the following value
	in the IANA "OAuth Authorization Server Metadata" registry <xref targe	in the "OAuth Authorization Server Metadata" registry <xref target="IANA.OAuth.P
	t="IANA.OAuth.Params"></xref>	arams"></xref>
	established by <xref target="RFC8414"></xref>.</t>	established by <xref target="RFC8414"></xref>.</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Metadata Name: <tt>dpop_signing_alg_values_supported</tt></li>	<dt>Metadata Name:</dt><dd><tt>dpop_signing_alg_values_supported</tt></dd>
	<li>Metadata Description: JSON array containing a list of the JWS algorithms su	<dt>Metadata Description:</dt><dd>JSON array containing a list of the JWS algori
	pported for DPoP proof JWTs</li>	thms supported for DPoP proof JWTs</dd>
	<li>Change Controller: IETF</li>	<dt>Change Controller:</dt><dd>IETF</dd>
	<li>Specification Document(s): [[ <xref target="as-meta"></xref> of this specif	<dt>Reference:</dt><dd><xref target="as-meta"></xref> of RFC 9449</dd>
	ication ]]</li>	</dl>
	</ul>
	</section>	</section>

	<section anchor="oauth-dynamic-client-registration-metadata"><name>OAuth Dynamic Client Registration Metadata</name>	<section anchor="oauth-dynamic-client-registration-metadata"><name>OAuth Dynamic Client Registration Metadata</name>

	<t>This specification requests registration of the following value	<t>IANA has registered the following value
	in the IANA "OAuth Dynamic Client Registration Metadata" registry <xre	in the IANA "OAuth Dynamic Client Registration Metadata" registry <xref target="
	f target="IANA.OAuth.Params"></xref>	IANA.OAuth.Params"></xref>
	established by <xref target="RFC7591"></xref>.</t>	established by <xref target="RFC7591"></xref>.</t>


	<ul spacing="compact">	<dl spacing="normal">
	<li>Metadata Name: <tt>dpop_bound_access_tokens</tt></li>	<dt>Client Metadata Name:</dt><dd><tt>dpop_bound_access_tokens</tt></dd>
	<li>Metadata Description: Boolean value specifying whether the client always us	<dt>Client Metadata Description:</dt><dd>Boolean value specifying whether the cl
	es DPoP for token requests</li>	ient always uses DPoP for token requests</dd>
	<li>Change Controller: IETF</li>	<dt>Change Controller:</dt><dd>IETF</dd>
	<li>Specification Document(s): [[ <xref target="client-meta"></xref> of this sp	<dt>Reference:</dt><dd><xref target="client-meta"></xref> of RFC 9449</dd>
	ecification ]]</li>	</dl>
	</ul>
	</section>	</section>
	</section>	</section>

	</middle>	</middle>

	<back>	<back>

	<references><name>Normative References</name>
		<displayreference target="I-D.ietf-oauth-security-topics" to="SECURITY-TOPICS"/>
		<displayreference target="I-D.ietf-oauth-token-binding" to="TOKEN-BINDING"/>

		<references>
		<name>References</name>
		<references>
		<name>Normative References</name>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3986. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3986. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5234. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5234. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6125. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6125. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6749. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6749. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6750. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6750. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7515. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7515. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7517. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7517. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7519. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7519. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7638. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7638. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7800. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7800. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174. xml"/>

	<reference anchor="SHS" target="https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS
	.180-4.pdf">	<reference anchor="SHS" target="http://dx.doi.org/10.6028/NIST.FIPS.180-4">
	<front>	<front>
	<title>Secure Hash Standard (SHS)</title>	<title>Secure Hash Standard (SHS)</title>
	<author>	<author>
	<organization>National Institute of Standards and Technology</organization >	<organization>National Institute of Standards and Technology</organization >
	</author>	</author>
	<date year="2015" month="August"></date>	<date year="2015" month="August"></date>
	</front>	</front>

	<format type="PDF" target="https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.18 0-4.pdf"></format>
	<seriesInfo name="FIPS" value="PUB 180-4"></seriesInfo>	<seriesInfo name="FIPS" value="PUB 180-4"></seriesInfo>

		<seriesInfo name="DOI" value="10.6028/NIST.FIPS.180-4"/>
	</reference>	</reference>
	</references>	</references>


	<references><name>Informative References</name>	<references><name>Informative References</name>


	<reference anchor="BREACH" target="https://cve.mitre.org/cgi-bin/cvename.cgi?nam e=CVE-2013-3587">	<reference anchor="BREACH" target="https://cve.mitre.org/cgi-bin/cvename.cgi?nam e=CVE-2013-3587">
	<front>	<front>
	<title>CVE-2013-3587</title>	<title>CVE-2013-3587</title>

	<author></author>	<author><organization>CVE</organization></author>
	</front>	</front>
	</reference>	</reference>


	<reference anchor="CRIME" target="https://cve.mitre.org/cgi-bin/cvename.cgi?name =cve-2012-4929">	<reference anchor="CRIME" target="https://cve.mitre.org/cgi-bin/cvename.cgi?name =cve-2012-4929">
	<front>	<front>
	<title>CVE-2012-4929</title>	<title>CVE-2012-4929</title>

	<author></author>	<author><organization>CVE</organization></author>
	</front>	</front>
	</reference>	</reference>


	<reference anchor="Cloudbleed" target="https://blog.cloudflare.com/incident-repo rt-on-memory-leak-caused-by-cloudflare-parser-bug/">	<reference anchor="Cloudbleed" target="https://blog.cloudflare.com/incident-repo rt-on-memory-leak-caused-by-cloudflare-parser-bug/">
	<front>	<front>
	<title>Incident report on memory leak caused by Cloudflare parser bug</title >	<title>Incident report on memory leak caused by Cloudflare parser bug</title >

	<author></author>	<author initials="J." surname="Graham-Cumming" fullname="John Graham-Cumming
		"/>
		<date month="February" year="2017"/>
	</front>	</front>
	</reference>	</reference>


	<reference anchor="GitHub.Tokens" target="https://github.blog/2022-04-15-securit y-alert-stolen-oauth-user-tokens/">	<reference anchor="GitHub.Tokens" target="https://github.blog/2022-04-15-securit y-alert-stolen-oauth-user-tokens/">
	<front>	<front>
	<title>Security alert: Attack campaign involving stolen OAuth user tokens is sued to two third-party integrators</title>	<title>Security alert: Attack campaign involving stolen OAuth user tokens is sued to two third-party integrators</title>

	<author></author>	<author initials="M." surname="Hanley" fullname="Mike Hanley"/>
		<date month="April" year="2022"/>
	</front>	</front>
	</reference>	</reference>


	<reference anchor="Heartbleed" target="https://cve.mitre.org/cgi-bin/cvename.cgi ?name=cve-2014-0160">	<reference anchor="Heartbleed" target="https://cve.mitre.org/cgi-bin/cvename.cgi ?name=cve-2014-0160">
	<front>	<front>
	<title>CVE-2014-0160</title>	<title>CVE-2014-0160</title>
	<author></author>	<author></author>
	</front>	</front>
	</reference>	</reference>


		<!-- [I-D.ietf-oauth-security-topics] IESG state I-D Exists as of 8/9/23 -->
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml-ids/reference.I-D.i etf-oauth-security-topics.xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml-ids/reference.I-D.i etf-oauth-security-topics.xml"/>


		<!-- [I-D.ietf-oauth-token-binding] IESG state Expired as of 8/9/23 -->
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml-ids/reference.I-D.i etf-oauth-token-binding.xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml-ids/reference.I-D.i etf-oauth-token-binding.xml"/>

	<reference anchor="IANA.HTTP.AuthSchemes" target="https://www.iana.org/assignmen
	ts/http-authschemes">	<reference anchor="IANA.HTTP.AuthSchemes" target="https://www.iana.org/assignmen
		ts/http-authschemes/">
	<front>	<front>
	<title>Hypertext Transfer Protocol (HTTP) Authentication Scheme Registry</ti tle>	<title>Hypertext Transfer Protocol (HTTP) Authentication Scheme Registry</ti tle>
	<author>	<author>
	<organization>IANA</organization>	<organization>IANA</organization>
	</author>	</author>
	</front>	</front>
	</reference>	</reference>

	<reference anchor="IANA.HTTP.Fields" target="https://www.iana.org/assignments/ht
	tp-fields/http-fields.xhtml">	<reference anchor="IANA.HTTP.Fields" target="https://www.iana.org/assignments/ht
		tp-fields/">
	<front>	<front>
	<title>Hypertext Transfer Protocol (HTTP) Field Name Registry</title>	<title>Hypertext Transfer Protocol (HTTP) Field Name Registry</title>
	<author>	<author>
	<organization>IANA</organization>	<organization>IANA</organization>
	</author>	</author>

	<date></date>
	</front>	</front>
	</reference>	</reference>

	<reference anchor="IANA.JOSE.ALGS" target="https://www.iana.org/assignments/jose
	/jose.xhtml#web-signature-encryption-algorithms">	<reference anchor="IANA.JOSE.ALGS" target="https://www.iana.org/assignments/jose
		/">
	<front>	<front>
	<title>JSON Web Signature and Encryption Algorithms</title>	<title>JSON Web Signature and Encryption Algorithms</title>
	<author>	<author>
	<organization>IANA</organization>	<organization>IANA</organization>
	</author>	</author>

	<date></date>
	</front>	</front>
	</reference>	</reference>

	<reference anchor="IANA.JWT" target="https://www.iana.org/assignments/jwt">
		<reference anchor="IANA.JWT" target="https://www.iana.org/assignments/jwt/">
	<front>	<front>
	<title>JSON Web Token Claims</title>	<title>JSON Web Token Claims</title>
	<author>	<author>
	<organization>IANA</organization>	<organization>IANA</organization>
	</author>	</author>

	<date></date>
	</front>	</front>
	</reference>	</reference>

	<reference anchor="IANA.MediaTypes" target="https://www.iana.org/assignments/med
	ia-types">	<reference anchor="IANA.MediaTypes" target="https://www.iana.org/assignments/med
		ia-types/">
	<front>	<front>
	<title>Media Types</title>	<title>Media Types</title>
	<author>	<author>
	<organization>IANA</organization>	<organization>IANA</organization>
	</author>	</author>
	</front>	</front>
	</reference>	</reference>

	<reference anchor="IANA.OAuth.Params" target="https://www.iana.org/assignments/o
	auth-parameters">	<reference anchor="IANA.OAuth.Params" target="https://www.iana.org/assignments/o
		auth-parameters/">
	<front>	<front>
	<title>OAuth Parameters</title>	<title>OAuth Parameters</title>
	<author>	<author>
	<organization>IANA</organization>	<organization>IANA</organization>
	</author>	</author>
	</front>	</front>
	</reference>	</reference>


	<reference anchor="OpenID.Core" target="https://openid.net/specs/openid-connect- core-1_0.html">	<reference anchor="OpenID.Core" target="https://openid.net/specs/openid-connect- core-1_0.html">
	<front>	<front>

	<title>OpenID Connect Core 1.0</title>	<title>OpenID Connect Core 1.0 incorporating errata set 1</title>
	<author fullname="Nat Sakimura" initials="N." surname="Sakimura">	<author fullname="Nat Sakimura" initials="N." surname="Sakimura">

	<organization></organization>
	</author>	</author>
	<author fullname="John Bradley" initials="J." surname="Bradley">	<author fullname="John Bradley" initials="J." surname="Bradley">

	<organization></organization>
	</author>	</author>

	<author fullname="Michael B. Jones" initials="M.B." surname="Jones">	<author fullname="Michael B. Jones" initials="M." surname="Jones">
	<organization></organization>
	</author>	</author>

	<author fullname="Breno de Medeiros" initials="B.d." surname="Medeiros">	<author fullname="Breno de Medeiros" initials="B." surname="de Medeiros">
	<organization></organization>
	</author>	</author>
	<author fullname="Chuck Mortimore" initials="C." surname="Mortimore">	<author fullname="Chuck Mortimore" initials="C." surname="Mortimore">

	<organization></organization>
	</author>	</author>
	<date year="2014" month="November"></date>	<date year="2014" month="November"></date>
	</front>	</front>
	</reference>	</reference>


	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2046. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2046. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4122. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4122. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4949. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4949. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6838. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6838. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7523. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7523. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7591. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7591. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7636. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7636. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7662. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7662. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8414. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8414. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8705. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8705. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8707. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8707. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8725. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8725. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8792. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8792. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9110. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9110. xml"/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9126. xml"/>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9126. xml"/>

	<reference anchor="W3C.CSP" target="https://www.w3.org/TR/2018/WD-CSP3-20181015/
	">	<reference anchor="W3C.CSP" target="https://www.w3.org/TR/CSP3/">
	<front>	<front>
	<title>Content Security Policy Level 3</title>	<title>Content Security Policy Level 3</title>
	<author fullname="Mike West" initials="M." surname="West">	<author fullname="Mike West" initials="M." surname="West">
	<organization></organization>	<organization></organization>
	</author>	</author>

	<date year="2018" month="October" day="15"></date>	<date year="2023" month="July"></date>
	</front>	</front>

	<format type="HTML" target="https://www.w3.org/TR/2018/WD-CSP3-20181015/"></fo	<refcontent>W3C Working Draft</refcontent>
	rmat>
	<seriesInfo name="World Wide Web Consortium Working Draft" value="WD-CSP3-2018
	1015"></seriesInfo>
	</reference>	</reference>


	<reference anchor="W3C.WebCryptoAPI" target="https://www.w3.org/TR/2017/REC-WebC ryptoAPI-20170126">	<reference anchor="W3C.WebCryptoAPI" target="https://www.w3.org/TR/2017/REC-WebC ryptoAPI-20170126">
	<front>	<front>
	<title>Web Cryptography API</title>	<title>Web Cryptography API</title>
	<author fullname="Mark Watson" initials="M." surname="Watson">	<author fullname="Mark Watson" initials="M." surname="Watson">
	<organization></organization>	<organization></organization>
	</author>	</author>

	<date year="2017" month="January" day="26"></date>	<date year="2017" month="January"></date>
	</front>	</front>

	<format type="HTML" target="https://www.w3.org/TR/2017/REC-WebCryptoAPI-201701	<refcontent>W3C Recommendation</refcontent>
	26"></format>
	<seriesInfo name="World Wide Web Consortium Recommendation" value="REC-WebCryp
	toAPI-20170126"></seriesInfo>
	</reference>	</reference>


	<reference anchor="WHATWG.Fetch" target="https://fetch.spec.whatwg.org/">	<reference anchor="WHATWG.Fetch" target="https://fetch.spec.whatwg.org/">
	<front>	<front>
	<title>Fetch Living Standard</title>	<title>Fetch Living Standard</title>

	<author fullname="WHATWG" surname="WHATWG">	<author>
	<organization>WHATWG</organization>	<organization>WHATWG</organization>
	</author>	</author>

	<date year="2022" month="May"></date>	<date year="2023" month="July"></date>
	</front>	</front>
	</reference>	</reference>
	</references>	</references>

		</references>
	<section anchor="Acknowledgements"><name>Acknowledgements</name>	<section anchor="Acknowledgements" numbered="false"><name>Acknowledgements</name
		>
	<t>We would like to thank	<t>We would like to thank

	Brock Allen,	<contact fullname="Brock Allen"/>,
	Annabelle Backman,	<contact fullname="Annabelle Backman"/>,
	Spencer Balogh,	<contact fullname="Dominick Baier"/>,
	Dominick Baier,	<contact fullname="Spencer Balogh"/>,
	Vittorio Bertocci,	<contact fullname="Vittorio Bertocci"/>,
	Jeff Corrigan,	<contact fullname="Jeff Corrigan"/>,
	Domingos Creado,	<contact fullname="Domingos Creado"/>,
	Andrii Deinega,	<contact fullname="Philippe De Ryck"/>,
	William Denniss,	<contact fullname="Andrii Deinega"/>,
	Vladimir Dzhuvinov,	<contact fullname="William Denniss"/>,
	Mike Engan,	<contact fullname="Vladimir Dzhuvinov"/>,
	Nikos Fotiou,	<contact fullname="Mike Engan"/>,
	Mark Haine,	<contact fullname="Nikos Fotiou"/>,
	Dick Hardt,	<contact fullname="Mark Haine"/>,
	Joseph Heenan,	<contact fullname="Dick Hardt"/>,
	Bjorn Hjelm,	<contact fullname="Joseph Heenan"/>,
	Jacob Ideskog,	<contact fullname="Bjorn Hjelm"/>,
	Jared Jennings,	<contact fullname="Jacob Ideskog"/>,
	Benjamin Kaduk,	<contact fullname="Jared Jennings"/>,
	Pieter Kasselman,	<contact fullname="Benjamin Kaduk"/>,
	Neil Madden,	<contact fullname="Pieter Kasselman"/>,
	Rohan Mahy,	<contact fullname="Neil Madden"/>,
	Karsten Meyer zu Selhausen,	<contact fullname="Rohan Mahy"/>,
	Nicolas Mora,	<contact fullname="Karsten Meyer zu Selhausen"/>,
	Steinar Noem,	<contact fullname="Nicolas Mora"/>,
	Mark Nottingham,	<contact fullname="Steinar Noem"/>,
	Rob Otto,	<contact fullname="Mark Nottingham"/>,
	Aaron Parecki,	<contact fullname="Rob Otto"/>,
	Michael Peck,	<contact fullname="Aaron Parecki"/>,
	Roberto Polli,	<contact fullname="Michael Peck"/>,
	Paul Querna,	<contact fullname="Roberto Polli"/>,
	Justin Richer,	<contact fullname="Paul Querna"/>,
	Joseph Salowey,	<contact fullname="Justin Richer"/>,
	Rifaat Shekh-Yusef,	<contact fullname="Joseph Salowey"/>,
	Filip Skokan,	<contact fullname="Rifaat Shekh-Yusef"/>,
	Dmitry Telegin,	<contact fullname="Filip Skokan"/>,
	Dave Tonge,	<contact fullname="Dmitry Telegin"/>,
	Jim Willeke,	<contact fullname="Dave Tonge"/>,
	Philippe De Ryck,	<contact fullname="Jim Willeke"/>,
	and others (please let us know, if you've been mistakenly omitted)	and others for their valuable input, feedback, and general support of this work.
	for their valuable input, feedback and general support of this work.</t>	</t>
	<t>This document originated from discussions at the 4th OAuth Security	<t>This document originated from discussions at the 4th OAuth Security
	Workshop in Stuttgart, Germany. We thank the organizers of this	Workshop in Stuttgart, Germany. We thank the organizers of this

	workshop (Ralf Kusters, Guido Schmitz).</t>	workshop (<contact fullname="Ralf Küsters"/> and <contact fullname="Guido Schmit
	</section>	z"/>).</t>

	<section anchor="document-history"><name>Document History</name>
	<t>[[ To be removed from the final specification ]]</t>
	<t>-16</t>

	<ul spacing="compact">
	<li>Per suggestion of the registry's designated expert, change "resource er
	ror response" to "resource access error response" for location of
	the two items in the "OAuth Extensions Error Registration" section</l
	i>
	</ul>
	<t>-15</t>

	<ul spacing="compact">
	<li>Editorial updates from IESG review/ballot</li>
	<li>Mike Jones and Daniel Fett with new email/organization info</li>
	</ul>
	<t>-14</t>

	<ul spacing="compact">
	<li>Add sec considerations sub-section about binding to client identity</li>
	<li>Explicitly say that nonces must be unpredictable</li>
	<li>Change to a numbered list in 'Checking DPoP Proofs'</li>
	<li>Editorial adjustments</li>
	<li>Incorporated HTTP header field definition and RFC 8792 '\' line wrapping sug
	gestions by Mark Nottingham</li>
	</ul>
	<t>-13</t>

	<ul spacing="compact">
	<li>Editorial updates/fixes</li>
	<li>Make sure RFC7519 is a normative reference</li>
	</ul>
	<t>-12</t>

	<ul spacing="compact">
	<li>Updates from Roman Danyliw's AD review</li>
	<li>DPoP-Nonce now included in HTTP header field registration request</li>
	<li>Fixed section reference to URI Scheme-Based Normalization</li>
	<li>Attempt to better describe the rationale for SHA-256 only and expectations f
	or how hash algorithm agility would be achieved if needed in the future</li>
	<li>Elaborate on the use of multiple WWW-Authenticate challenges by protected re
	sources</li>
	<li>Fix access token request examples that were missing a client_id</li>
	</ul>
	<t>-11</t>

	<ul spacing="compact">
	<li>Updates addressing outstanding shepherd review comments per side meeting dis
	cussions at IETF 114</li>
	<li>Added more explanation of the PAR considerations</li>
	<li>Added parenthetical remark "(such as ES256)" to Signature Algorith
	ms subsection</li>
	<li>Added more explanation for ath</li>
	<li>Added a reference to RFC8725 in mention of explicit JWT typing</li>
	</ul>
	<t>-10</t>

	<ul spacing="compact">
	<li>Updates addressing some shepherd review comments</li>
	<li>Update HTTP references as RFCs 723x have been superseded by RFC 9110</li>
	<li>Editorial fixes</li>
	<li>Added some clarifications, etc. around nonce</li>
	<li>Added client considerations subsection</li>
	<li>Use bullets rather than numbers in Checking DPoP Proofs so as not to imply s
	pecific order</li>
	<li>Added notes/reminders about browser-based client applications using CORS nee
	ding access to response headers</li>
	<li>Added a JWT claims registry update request for "nonce" to (better)
	allow for more general use in other contexts</li>
	</ul>
	<t>-09</t>

	<ul spacing="compact">
	<li>Add note/reminder about browser-based client applications using CORS needing
	access to response headers.</li>
	<li>Fixed typo</li>
	</ul>
	<t>-08</t>

	<ul spacing="compact">
	<li>Lots of editorial updates from WGLC feedback</li>
	<li>Further clarify that either iat or nonce can be used alone in validating the
	timeliness of the proof and somewhat de-emphasize jti tracking</li>
	</ul>
	<t>-07</t>

	<ul spacing="compact">
	<li>Registered the <tt>application/dpop+jwt</tt> media type.</li>
	<li>Editorial updates/clarifications based on review feedback.</li>
	<li>Added "(on the order of seconds or minutes)" to somewhat qualify &
	quot;relatively brief period" and "reasonably near future" and gi
	ve a general idea of expected timeframe without being overly prescriptive.</li>
	<li>Added a step to <xref target="checking"></xref> to reiterate that the jwk he
	ader cannot have a private key.</li>
	</ul>
	<t>-06</t>

	<ul spacing="compact">
	<li>Editorial updates and fixes</li>
	<li>Changed name of client metadata parameter to <tt>dpop_bound_access_tokens</t
	t></li>
	</ul>
	<t>-05</t>

	<ul spacing="compact">
	<li>Added Authorization Code binding via the <tt>dpop_jkt</tt> parameter.</li>
	<li>Described the authorization code reuse attack and how <tt>dpop_jkt</tt> miti
	gates it.</li>
	<li>Enhanced description of DPoP proof expiration checking.</li>
	<li>Described nonce storage requirements and how nonce mismatches and missing no
	nces are self-correcting.</li>
	<li>Specified the use of the <tt>use_dpop_nonce</tt> error for missing and misma
	tched nonce values.</li>
	<li>Specified that authorization servers use <tt>400 (Bad Request)</tt> errors t
	o supply nonces and resource servers use <tt>401 (Unauthorized)</tt> errors to d
	o so.</li>
	<li>Added a bit more about <tt>ath</tt> and pre-generated proofs to the security
	considerations.</li>
	<li>Mentioned confirming the DPoP binding of the access token in the list in <xr
	ef target="checking"></xref>.</li>
	<li>Added the <tt>always_uses_dpop</tt> client registration metadata parameter.<
	/li>
	<li>Described the relationship between DPoP and Pushed Authorization Requests (P
	AR).</li>
	<li>Updated references for drafts that are now RFCs.</li>
	</ul>
	<t>-04</t>

	<ul spacing="compact">
	<li>Added the option for a server-provided nonce in the DPoP proof.</li>
	<li>Registered the <tt>invalid_dpop_proof</tt> and <tt>use_dpop_nonce</tt> error
	codes.</li>
	<li>Removed fictitious uses of <tt>realm</tt> from the examples, as they added n
	o value.</li>
	<li>State that if the introspection response has a <tt>token_type</tt>, it has t
	o be <tt>DPoP</tt>.</li>
	<li>Mention that RFC7235 allows multiple authentication schemes in <tt>WWW-Authe
	nticate</tt> with a 401.</li>
	<li>Editorial fixes.</li>
	</ul>
	<t>-03</t>

	<ul spacing="compact">
	<li>Add an access token hash (<tt>ath</tt>) claim to the DPoP proof when used in
	conjunction with the presentation of an access token for protected resource acc
	ess</li>
	<li>add Untrusted Code in the Client Context section to security considerations<
	/li>
	<li>Editorial updates and fixes</li>
	</ul>
	<t>-02</t>

	<ul spacing="compact">
	<li>Lots of editorial updates and additions including expanding on the objective
	s,
	better defining the key confirmation representations, example updates and addit
	ions,
	better describing mixed bearer/dpop token type deployments, clarify RT binding
	only being
	done for public clients and why, more clearly allow for a bound RT but with bea
	rer AT,
	explain/justify the choice of SHA-256 for key binding, and more</li>
	<li>Require that a protected resource supporting bearer and DPoP at the same tim
	e
	must reject an access token received as bearer, if that token is DPoP-bound</li
	>
	<li>Remove the case-insensitive qualification on the <tt>htm</tt> claim check</l
	i>
	<li>Relax the jti tracking requirements a bit and qualify it by URI</li>
	</ul>
	<t>-01</t>

	<ul spacing="compact">
	<li>Editorial updates</li>
	<li>Attempt to more formally define the DPoP Authorization header scheme</li>
	<li>Define the 401/WWW-Authenticate challenge</li>
	<li>Added <tt>invalid_dpop_proof</tt> error code for DPoP errors in token reques
	t</li>
	<li>Fixed up and added to the IANA section</li>
	<li>Added <tt>dpop_signing_alg_values_supported</tt> authorization server metada
	ta</li>
	<li>Moved the Acknowledgements into an Appendix and added a bunch of names (best
	effort)</li>
	</ul>
	<t>-00 [[ Working Group Draft ]]</t>

	<ul spacing="compact">
	<li>Working group draft</li>
	</ul>
	<t>-04</t>

	<ul spacing="compact">
	<li>Update OAuth MTLS reference to RFC 8705</li>
	<li>Use the newish RFC v3 XML and HTML format</li>
	</ul>
	<t>-03</t>

	<ul spacing="compact">
	<li>rework the text around uniqueness requirements on the jti claim in the DPoP
	proof JWT</li>
	<li>make tokens a bit smaller by using <tt>htm</tt>, <tt>htu</tt>, and <tt>jkt</
	tt> rather than <tt>http_method</tt>, <tt>http_uri</tt>, and <tt>jkt#S256</tt> r
	espectively</li>
	<li>more explicit recommendation to use mTLS if that is available</li>
	<li>added David Waite as co-author</li>
	<li>editorial updates</li>
	</ul>
	<t>-02</t>

	<ul spacing="compact">
	<li>added normalization rules for URIs</li>
	<li>removed distinction between proof and binding</li>
	<li>"jwk" header again used instead of "cnf" claim in DPoP p
	roof</li>
	<li>renamed "Bearer-DPoP" token type to "DPoP"</li>
	<li>removed ability for key rotation</li>
	<li>added security considerations on request integrity</li>
	<li>explicit advice on extending DPoP proofs to sign other parts of the HTTP mes
	sages</li>
	<li>only use the jkt#S256 in ATs</li>
	<li>iat instead of exp in DPoP proof JWTs</li>
	<li>updated guidance on token_type evaluation</li>
	</ul>
	<t>-01</t>

	<ul spacing="compact">
	<li>fixed inconsistencies</li>
	<li>moved binding and proof messages to headers instead of parameters</li>
	<li>extracted and unified definition of DPoP JWTs</li>
	<li>improved description</li>
	</ul>
	<t>-00</t>

	<ul spacing="compact">
	<li>first draft</li>
	</ul>
	</section>	</section>


	</back>	</back>


	</rfc>	</rfc>

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