INTERNET-DRAFT Donald Eastlake 3rd Motorola Expires: October 2001 April 2001 Additional XML Digital Signature URIs ---------- --- ------- --------- ---- Status of This Document Distribution of this draft, which is intended to become an Informational RFC, is unlimited. Comments should be sent to the author or the XMLDSIG working group . This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract A number of algorithm URIs intended for use with XML Digital Signatures are defined. D. Eastlake 3rd [Page 1] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 Table of Contents Status of This Document....................................1 Copyright Notice...........................................1 Abstract...................................................1 Table of Contents..........................................2 1. Introduction............................................3 2. URIs....................................................3 2.1 Message Digests........................................3 2.1.1 MD5..................................................3 2.1.2 SHA-256..............................................4 2.1.3 SHA-512..............................................4 2.1.4 SHA-384..............................................4 2.2 Message Authentication Codes...........................5 2.2.1 HMAC-MD5.............................................5 2.2.2 HMAC-SHA-256.........................................6 2.2.3 HMAC-SHA-512.........................................6 2.2.4 HMAC-SHA-384.........................................6 2.3 Signature Algorithms...................................7 2.3.1 RSA-MD5..............................................7 2.3.2 RSA-SHA-256..........................................7 2.3.3 RSA-SHA-512..........................................7 2.3.4 RSA-SHA-384..........................................7 2.4 Canonicalizaton Algorithms.............................7 2.4.1 Minimal Canonicalization.............................7 2.5 Transform Algorithms...................................8 3. IANA Considerations.....................................8 4. Security Considerations.................................8 References.................................................9 Authors Addresses..........................................9 Full Copyright Statement..................................10 Expiration and File Name..................................10 D. Eastlake 3rd [Page 2] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 1. Introduction XML Digital Signatures have been standardized by the joint IETF/W3C XMLDSIG working group. The Proposed Standard is specified in [RFC 3075]. In addition, Canonical XML, which is used by many digital signatures, has been standardized by the W3C and is documented in Informational [RFC 3076]. [RFC 3075] specifies URIs to identify algorithms. However, this ppotocol is likely to be raised to Draft Standard soon, which requires two independent interoperable implementations to exist. This may require algorithms in which there appears to be substantial interest to be dropped. This document is intended as a convenient reference list of URIs and descriptions for any dropped from the Proposed Standard due to lack of implementations plus additional suggested algorithms in which there appears to be substantial interest. 2. URIs The sections below parallel those in Section 6 of RFC 3075 which group various algorithms by there use in XML Digital Sigantures. 2.1 Message Digests 2.1.1 MD5 Identifier: http://md.xmldsig.ietf.arpa#md5 The MD5 algorithm [RFC 1321] takes no explicit parameters. An example of an MD5 DigestAlgorithm element is: An MD5 digest is a 128-bit string. The content of the DigestValue element shall be the base64 [RFC 2045] encoding of this bit string viewed as a 16-octet octet stream. D. Eastlake 3rd [Page 3] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 2.1.2 SHA-256 Identifier: http://md.xmldsig.ietf.arpa#sha256 The SHA-256 algorithm [SHA-256] takes no explicit parameters. An example of a SHA-256 DigestAlgorithm element is: 400 A SHA-512 digest is a 512 bit string except that, if the SHA512truncation parameter is present specifying truncation to n bits, it is the left most n bits of that string. In effect, the truncation parameter defaults to 512. Schema Definition: DTD: 2.1.4 SHA-384 Identifier: http://md.xmldsig.ietf.arpa#sha384 The SHA-384 algorithm [SHA-384] takes an optional truncation D. Eastlake 3rd [Page 4] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 parameter, SHAtruncation, in the range 0 to 512. An example of a SHA-384 DigestAlforithm element without such a parameter is: A SHA-384 digest is the leftmost 384 bits of the 512 bit string that the algorithm calculates internally except that, if the SHAtruncation parameter is present specifying truncation to n bits, it is the left most n bits of that string. In effect, the truncation parameter defaults to 384. (The SHA-384 algorithm has the same internal structure as the SHA-512 algorithm but a few different constants are used, resulting in a different 512 bit hasj value, and it is normally truncated to 384 bits. See Schema Definition and DTD for SHA-512 above. 2.2 Message Authentication Codes Some text in this section is duplicated from RFC 3075 for the convenience of the reader. 2.2.1 HMAC-MD5 Identifier: http://mac.xmldsig.ietf.arpa#hmac-md5 The HMAC algorithm (RFC2104 [HMAC]) takes the truncation length in bits as a parameter; if the parameter is not specified then all the bits of the hash are output. An example of an HMAC SignatureMethod element: 112 The output of the HMAC algorithm is ultimately the output (possibly truncated) of the chosen digest algorithm. This value shall be base64 encoded in the same straightforward fashion as the output of the digest algorithms. Example: the SignatureValue element for the HMAC- MD5 digest 9294727A 3638BB1C 13F48EF8 158BFC9D from the test vectors in [RFC 2104] would be D. Eastlake 3rd [Page 5] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 kpRyejY4uxwT9I74FYv8nQ== Schema Definition: DTD: The Schema Definition and DTD immediately above are copied from RFC 3075. Although some cryptographic suspicions have recently been cast on MD5 for use in signatures such as RSA-MD5 below, this does not effect use of MD5 in HMAC. 2.2.2 HMAC-SHA-256 Identifier: http://mac.xmldsig.ietf.arpa#hmac-sha256 SHA-256 [SHA-256] can also be used in HMAC as described in section 2.2.1 above. 2.2.3 HMAC-SHA-512 Identifier: http://mac.xmldsig.ietf.arpa#hmac-sha512 SHA-512 [SHA-512] can also be used in HMAC as describe in section 2.2.1 above. 2.2.4 HMAC-SHA-384 Identifier: http://mac.xmldsig.ietf.arpa#hmac-sha384 SHA-384 [SHA-384] can also be used in HMAC as described in section 2.2.1 above. D. Eastlake 3rd [Page 6] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 2.3 Signature Algorithms 2.3.1 RSA-MD5 Identifier: http://sig.xmldsig.ietf.arpa#rsa-md5 Due to increases in computer processor power and advances in cryptography, use of RSA-MD5 is not recommended. 2.3.2 RSA-SHA-256 Identifier: http://sig.xmldsig.ietf.arpa#rsa-sha256 2.3.3 RSA-SHA-512 Identifier: http://sig.xmldsig.ietf.arpa#rsa-sha512 2.3.4 RSA-SHA-384 Identifier: http://sig.xmldsig.ietf.arpa#rsa-sha384 2.4 Canonicalizaton Algorithms 2.4.1 Minimal Canonicalization At this time there are not two independent interoperable implementations of Minimal Canonicalization. Therefore, when XML Digital Siganture is advanced from Proposed Standard to Draft Standard, it must be dropped from the standard track documents. However, there is still substantial interest and indicates of possible future use for Minimal Canonicalization which can be found in [RFC 3075], Section 6.5.1. For reference, it's identifier is: D. Eastlake 3rd [Page 7] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 http://www.w3.org/2000/09/xmldsig#minimal 2.5 Transform Algorithms None included at present. (Java?) 3. IANA Considerations TBD. 4. Security Considerations TBD. D. Eastlake 3rd [Page 8] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 References [RFC 1321] - "The MD5 Message-Digest Algorithm", R. Rivest, April 1992. [RFC 2104] - "HMAC: Keyed-Hashing for Message Authentication", H. Krawczyk, M. Bellare, R. Canetti, February 1997. [RC 2045] - "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", N. Freed, N. Borenstein, November 1996. [RFC 3075] - "XML-Signature Syntax and Processing", D. Eastlake, J. Reagle, D. Solo, March 2001. [RFC 3076] - "Canonical XML Version 1.0", J. Boyer, March 2001. [SHA-256] - [SHA-384] - [SHA-512] - Authors Addresses Donald E. Eastlake 3rd Motorola 155 Beaver Street Milford, MA 01757 USA Telephone: +1-508-634-2066 (h) +1-508-261-5434 (w) FAX: +1-508-261-4447 (w) EMail: Donald.Eastlake@motorola.com D. Eastlake 3rd [Page 9] INTERNET-DRAFT Additional XMLDSIG URIs April 2001 Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Expiration and File Name This draft expires October 2001. Its file name is draft-eastlake-xmldsig-uri-00.txt. D. Eastlake 3rd [Page 10]