INTERNET-DRAFT HMAC-SHA TSIG Identifiers Donald E. Eastlake 3rd Motorola Expires: April 2004 October 2003 HMAC SHA TSIG Algorithm Identifiers ---- --- ---- --------- ----------- Donald E. Eastlake 3rd Status of This Document This draft is intended to be become a Proposed Standard RFC. Distribution of this document is unlimited. Comments should be sent to the author. 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. Abstract Use of the TSIG DNS resource record requires specification of a cryptogrpahic message authentication code. Currently idenfitiers have been specified only for the HMAC-MD5 and GSS TSIG algorithms. This document specifies identifiers for additional HMAC SHA TSIG algorithms. D. Eastlake 3rd [Page 1] INTERNET-DRAFT HMAC-SHA TSIG Identifiers Table of Contents Status of This Document....................................1 Abstract...................................................1 Table of Contents..........................................2 1. Introduction............................................3 2. Algorithms and Identifiers..............................4 3. IANA Considerations.....................................5 4. Security Considerations.................................5 References.................................................5 Author's Address...........................................6 Expiration and File Name...................................6 D. Eastlake 3rd [Page 2] INTERNET-DRAFT HMAC-SHA TSIG Identifiers 1. Introduction [RFC 2845] specifies a TSIG Resource Record that can be used to authenticate DNS queries and responses. This RR contains a domain name syntax data item which names the authentication algorithm used. [RFC 2845] defines the HMAC-MD5.SIG-ALG.REG.INT name for authentication codes using the HMAC [RFC 2104] algorithm with the MD5 [RFC 1321] hash algorithm. IANA has also registered "gss-tsig" as an identifier for TSIG authentication where the cryptographic operations are delegated to GSS [RFC gsstsig]. This document specifies additional names for TSIG authentication algorithms based on US NIST SHA algorithms, HMAC, and truncation. D. Eastlake 3rd [Page 3] INTERNET-DRAFT HMAC-SHA TSIG Identifiers 2. Algorithms and Identifiers TSIG Resource Records (RRs) [RFC 2845] are used to authenticate DNS queries and responses. They are intended to be efficient symmetric authentication codes based on a shared secret. (Asymmetric signatures can be provided using the SIG RR [RFC 2931].) Used with a strong hash function, HMAC [RFC 2104] provides a way to calculate such symmetric authentication codes. The only specified HMAC based TSIG algorithm identifier has been HMAC-MD5.SIG-ALG.REG.INT based on MD5 [RFC 1321]. However, MD5 is beginning to show its age and some signs of weakness have been found. While these particular weaknesses should have no effect on MD5 use with HMAC, identifiers are defined herein for using more recent hash functions which are believed to be stronger. In particular, SHA-1 [FIPS 180-1, RFC 3174], which is a 160 bit hash as compared with the 128 bits for MD5, and additional hash algorithms in the SHA family [FIPS 180-2] with 256, 384, and 512 bits, may be preferred in some case. Use of TSIG between a DNS resolver and server is by mutual agreement which agreement can include the support of additonal algorithms. In some cases, it is reasonable to truncate the output of HMAC and use the truncated value for authentication. Since the syntax for TSIG algorithm identifiers is that of a domain name, this is indicated in these identifiers by a leading decimal lable which gives the truncated length in bits. When truncation occurs, the bits used are the initial bits, trailing bits being discarded. For completeness in relation to HMAC based algorithms, the current HMAC-MD5.SIG-ALG.REG.INT identifier is included in the table below. Mandatory HMAC-MD5.SIG-ALG.REG.INT Recommended sha1 Recommended 96.sha1 Optional sha256 Optional 192.sha256 Optional sha384 Optional 320.sha384 Optional sha512 Optional 448.sha512 D. Eastlake 3rd [Page 4] INTERNET-DRAFT HMAC-SHA TSIG Identifiers 3. IANA Considerations This document, on approval by IETF Consensus [RFC 2434], registers the new TSIG algorithm identifiers listed in Section 2 with IANA. 4. Security Considerations For all of the message authentication code algorithms listed herein, those producing longer values are believed to be stronger. See Security Considerations section of [RFC 2845]. References [FIPS 180-1] - Secure Hash Standard, (SHA-1) US Federal Information Processing Standard, 17 April 1995. [FIPS 180-2] - Secure Hahs Standard, (SHA-1/256/384/512) US Federal Information Processing Standard, Draft, not yet issued. [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. [RFC 2434] - Guidelines for Writing an IANA Considerations Section in RFCs, T. Narten, H. Alvestrand, October 1998. [RFC 2845] - Secret Key Transaction Authentication for DNS (TSIG), P. Vixie, O. Gudmundsson, D. Eastlake, B. Wellington, May 2000. [RFC 2931] - DNS Request and Transaction Signatures ( SIG(0)s), D. Eastlake. September 2000. [RFC 3174] - US Secure Hash Algorithm 1 (SHA1), D. Eastlake, 3rd, P. Jones, September 2001. [RFC gsstsig] - GSS Algorthm for TSIG (GSS-TSIG), S. Kwan, P. Garg, J. Gilroy, L. Esibov, J. Westhead, R. Hall, draft-ietf-dnsext-gss- tsig-06.txt which ise in the RFC Editor queue. D. Eastlake 3rd [Page 5] INTERNET-DRAFT HMAC-SHA TSIG Identifiers Author's Address Donald E. Eastlake 3rd Motorola 155 Beaver Street Milford, MA 01757 USA Telephone: +1-508-786-7554 (w) +1-508-634-2066 (h) EMail: Donald.Eastlake@motorola.com Expiration and File Name This draft expires in April 2004. Its file name is draft-eastlake-tsig-sha-02.txt D. Eastlake 3rd [Page 6]