Additional Methods for Generating Key Identifiers Values
RFC 7093

 
Document Type RFC - Informational (December 2013; No errata)
Last updated 2013-12-20
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Independent Submission                                         S. Turner
Request for Comments: 7093                                          IECA
Category: Informational                                          S. Kent
ISSN: 2070-1721                                                      BBN
                                                               J. Manger
                                                                 Telstra
                                                           December 2013

        Additional Methods for Generating Key Identifiers 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) certificate extensions.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7093.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
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Turner, et al.                Informational                     [Page 1]
RFC 7093               Additional Examples For KIs         December 2013

1.  Introduction

   [RFC5280] defines the AKI (Authority Key Identifier) and SKI (Subject
   Key Identifier) certificate extensions.  [RFC5280] describes two
   example mechanisms for generating 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
   critical to security.  This document defines three additional
   mechanisms for generating Key Identifier values using SHA-256,
   SHA-384, and SHA-512 [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 of
      the SubjectPublicKeyInfo value.

Turner, et al.                Informational                     [Page 2]
RFC 7093               Additional Examples For KIs         December 2013

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:
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