wdiff rfc7093.original rfc7093.txt

Network Working Group
Independent Submission S. Turner
Internet-Draft
Request for Comments: 7093 IECA
Intended Status:
Category: Informational S. Kent
Expires: April 22, 2014
ISSN: 2070-1721 BBN
J. Manger
Telstra
October 19,
December 2013

Additional Methods for Generating Subject Key Identifiers
draft-turner-additional-methods-4kis-11.txt Values

Abstract

This document specifies additional example methods for generating Key
Identifier values for use in the AKI (Authority Key Identifier) and
SKI (Subject Key Identifier). Identifier) certificate extensions.

Status of this This Memo

This Internet-Draft document is submitted in full conformance with not an Internet Standards Track specification; it is
published for informational purposes.

This is a contribution to the
provisions RFC Series, independently of BCP 78 any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and BCP 79.

Internet-Drafts makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are working documents not a candidate for any level of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list
Standard; see Section 2 of RFC 5741.

Information about the current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum status of six months this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
http://www.rfc-editor.org/info/rfc7093.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

1. Introduction

[RFC5280] defines the AKI (Authority Key Identifier) and SKI (Subject
Key Identifier) certificate extensions. [RFC5280] describes two
example mechanisms for generating AKI/SKI AKI and SKI values: a 160-bit SHA-1
(Secure Hash Algorithm) hash of the public key and a four-bit type
field with the value 0100 followed by the least significant 60 bits
of the SHA-1 hash. Both of these mechanisms were designed to not be non-
security critical.
critical to security. This document defines three additional
mechanisms for generating Key Identifier values, values using SHA-256,
SHA-384, and SHA-512 [SHS], [SHS] that are similar to those examples defined
in [RFC5280] as well as one based on hashing the certificate's
Subject Public Key Info field.

2. Additional Methods for Generating Key Identifiers

[RFC5280] specifies two examples for generating key identifiers from
public keys. Four additional mechanisms are as follows:

1) The keyIdentifier is composed of the leftmost 160-bits of the
SHA-256 hash of the value of the BIT STRING subjectPublicKey
(excluding the tag, length, and number of unused bits).

2) The keyIdentifier is composed of the leftmost 160-bits of the
SHA-384 hash of the value of the BIT STRING subjectPublicKey
(excluding the tag, length, and number of unused bits).

3) The keyIdentifier is composed of the leftmost 160-bits of the
SHA-512 hash of the value of the BIT STRING subjectPublicKey
(excluding the tag, length, and number of unused bits).

4) The keyIdentifier is composed of the hash of the DER-encoding DER encoding of
the SubjectPublicKeyInfo value.

3. Examples

This section provides some examples. The keys and SKIs are presented
in hexadecimal (two hex digits per byte).

Given the following DER-encoded SubjectPublicKeyInfo value holding an
P-256 ECDSA (Elliptic Curve Digital Signature Algorithm) key:

30 59
30 13
06 07 2A8648CE3D0201 -- id-ecPublicKey
06 08 2A8648CE3D030107 -- secp256r1
03 42 00
04 7F7F35A79794C950060B8029FC8F363A
28F11159692D9D34E6AC948190434735
F833B1A66652DC514337AFF7F5C9C75D
670C019D95A5D639B72744C64A9128BB

The SHA-256 hash of the 65 bytes 047F7F...BB is:
BF37B3E5808FD46D54B28E846311BCCE1CAD2E1A62AA9092EF3EFB3F11451F44

The SHA-1 hash of these 65 bytes is:
6FEF9162C0A3F2E7608956D41C37DA0C8E87F0AE

The SHA-256 hash of the 91 bytes 305930...BB is:
6D20896AB8BD833B6B66554BD59B20225D8A75A296088148399D7BF763D57405

Using method 1 from section Section 2, the subjectKeyIdentifier would be:

30 1D
06 03 551D0E -- id-ce-subjectKeyIdentifier
04 16
04 14 BF37B3E5808FD46D54B28E846311BCCE1CAD2E1A

Using method 4 from section Section 2 with SHA-256 and no truncation, the
subjectKeyIdentifier extensions would be:

30 29
06 03 551D0E -- id-ce-subjectKeyIdentifier
04 22
04 20 6D20896AB8BD833B6B66554BD59B2022
5D8A75A296088148399D7BF763D57405

4. Security Considerations

The security considerations of [RFC5280] apply to certificates. The
security considerations of [RFC5758] apply to the hash algorithms.

While hash algorithms provide preimage resistance, second-preimage
resistance, and collision resistance, none of these properties are
needed for key identifiers.

6. IANA Considerations

None.

5. Acknowledgements

The authors wish to thank Santosh Chokhani, Stephen Farrell, Tom
Gindin, Peter Gutmann, Henry Holtz, David Kemp, Timothy Miller,
Michael StJohns, Stefan Santesson, Jim Schaad, Rene Struik, Koichi
Sugimoto, and Carl Wallace for taking the time to participate in the
discussions about this document. The discussions resulted in
numerous editorial and technical changes to the document.

8. References

8.1.

6. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.

[RFC5758] Dang, Q., Santesson, S., Moriarty, K., Brown, D., and T.
Polk, "Internet X.509 Public Key Infrastructure:
Additional Algorithms and Identifiers for DSA and ECDSA",
RFC 5758, January 2010.

[SHS] National Institute of Standards and Technology (NIST),
FIPS Publication 180-3: Secure Hash Standard, October
2008.

8.2. Informative References

None

Authors' Addresses

Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA

EMail: turners@ieca.com

Stephen Kent
BBN Technologies
10 Moulton St.
Cambridge, MA 02138
USA

EMail: kent@bbn.com

James Manger
Telstra
6 / 150 Lonsdale Street
Melbourne, Victoria 3000
Australia

Email:

EMail: james.h.manger@team.telstra.com