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337 lines
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DNSext Working Group F. Dupont
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Internet-Draft ISC
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Updates: 2845,2930,4635 May 8, 2009
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(if approved)
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Intended status: Standards Track
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Expires: November 9, 2009
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Deprecation of HMAC-MD5 in DNS TSIG and TKEY Resource Records
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draft-ietf-dnsext-tsig-md5-deprecated-03.txt
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Status of this Memo
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This Internet-Draft is submitted to IETF in full conformance with the
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provisions of BCP 78 and BCP 79. This document may contain material
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from IETF Documents or IETF Contributions published or made publicly
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available before November 10, 2008. The person(s) controlling the
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copyright in some of this material may not have granted the IETF
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Trust the right to allow modifications of such material outside the
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IETF Standards Process. Without obtaining an adequate license from
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the person(s) controlling the copyright in such materials, this
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document may not be modified outside the IETF Standards Process, and
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derivative works of it may not be created outside the IETF Standards
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Process, except to format it for publication as an RFC or to
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translate it into languages other than English.
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Internet-Drafts are working documents of the Internet Engineering
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Task Force (IETF), its areas, and its working groups. Note that
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other groups may also distribute working documents as Internet-
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Drafts.
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Internet-Drafts are draft documents valid for a maximum of six months
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and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
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material or to cite them other than as "work in progress."
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The list of current Internet-Drafts can be accessed at
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http://www.ietf.org/ietf/1id-abstracts.txt.
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The list of Internet-Draft Shadow Directories can be accessed at
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http://www.ietf.org/shadow.html.
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This Internet-Draft will expire on November 9, 2009.
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Copyright Notice
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Copyright (c) 2009 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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Dupont Expires November 9, 2009 [Page 1]
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Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009
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This document is subject to BCP 78 and the IETF Trust's Legal
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Provisions Relating to IETF Documents in effect on the date of
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publication of this document (http://trustee.ietf.org/license-info).
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Please review these documents carefully, as they describe your rights
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and restrictions with respect to this document.
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Abstract
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The main purpose of this document is to deprecate the use of HMAC-MD5
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as an algorithm for the TSIG (secret key transaction authentication)
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resource record in the DNS (domain name system), and the use of MD5
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in TKEY (secret key establishment for DNS).
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1. Introduction
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The secret key transaction authentication for DNS (TSIG, [RFC2845])
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was defined with the HMAC-MD5 [RFC2104] cryptographic algorithm.
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When the MD5 [RFC1321] security came to be considered lower than
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expected, [RFC4635] standardized new TSIG algorithms based on SHA
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[RFC3174][RFC3874][RFC4634] digests.
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But [RFC4635] did not deprecate the HMAC-MD5 algorithm. This
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document is targeted to complete the process, in detail:
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1. Mark HMAC-MD5.SIG-ALG.REG.INT as optional in the TSIG algorithm
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name registry managed by the IANA under the IETF Review Policy
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[RFC5226]
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2. Make HMAC-MD5.SIG-ALG.REG.INT support "not Mandatory" for
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implementations
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3. Provide a keying material derivation for the secret key
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establishment for DNS (TKEY, [RFC2930]) using a Diffie-Hellman
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exchange with SHA256 [RFC4634] in place of MD5 [RFC1321]
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4. Finally recommend the use of HMAC-SHA256.
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in [RFC2119].
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2. Implementation Requirements
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The table of section 3 of [RFC4635] is replaced by:
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Dupont Expires November 9, 2009 [Page 2]
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Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009
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+-------------------+--------------------------+
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| Requirement Level | Algorithm Name |
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+-------------------+--------------------------+
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| Optional | HMAC-MD5.SIG-ALG.REG.INT |
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| Optional | gss-tsig |
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| Mandatory | hmac-sha1 |
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| Optional | hmac-sha224 |
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| Mandatory | hmac-sha256 |
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| Optional | hmac-sha384 |
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| Optional | hmac-sha512 |
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+-------------------+--------------------------+
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Implementations that support TSIG MUST also implement HMAC-SHA1 and
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HMAC-SHA256 (i.e., algorithms at the "Mandatory" requirement level)
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and MAY implement GSS-TSIG and the other algorithms listed above
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(i.e., algorithms at a "not Mandatory" requirement level).
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3. TKEY keying material derivation
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When the TKEY [RFC2930] uses a Diffie-Hellman exchange, the keying
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material is derived from the shared secret and TKEY resource record
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data using MD5 [RFC1321] at the end of section 4.1 page 9.
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This is amended into:
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keying material =
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XOR ( DH value, SHA256 ( query data | DH value ) |
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SHA256 ( server data | DH value ) )
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using the same conventions.
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4. IANA Consideration
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This document extends the "TSIG Algorithm Names - per [] and
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[RFC2845]" located at
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http://www.iana.org/assignments/tsig-algorithm-names by adding a new
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column to the registry "Compliance Requirement".
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The registry should contain the following:
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Dupont Expires November 9, 2009 [Page 3]
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Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009
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+--------------------------+------------------------+-------------+
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| Algorithm Name | Compliance Requirement | Reference |
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+--------------------------+------------------------+-------------+
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| gss-tsig | Optional | [RFC3645] |
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| HMAC-MD5.SIG-ALG.REG.INT | Optional | [][RFC2845] |
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| hmac-sha1 | Mandatory | [RFC4635] |
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| hmac-sha224 | Optional | [RFC4635] |
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| hmac-sha256 | Mandatory | [RFC4635] |
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| hmac-sha384 | Optional | [RFC4635] |
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| hmac-sha512 | Optional | [RFC4635] |
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+--------------------------+------------------------+-------------+
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where [] is this document.
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5. Availability Considerations
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MD5 is no longer universally available and its use may lead to
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increasing operation issues. SHA1 is likely to suffer from the same
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kind of problem. In summary MD5 has reached end-of-life and SHA1
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will likely follow in the near term.
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According to [RFC4635], implementations which support TSIG are
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REQUIRED to implement HMAC-SHA256.
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6. Security Considerations
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This document does not assume anything about the cryptographic
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security of different hash algorithms. Its purpose is a better
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availability of some security mechanisms in a predictable time frame.
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Requirement levels are adjusted for TSIG and related specifications
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(i.e., TKEY):
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The support of HMAC-MD5 is changed from mandatory to optional.
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The use of MD5 and HMAC-MD5 is NOT RECOMMENDED.
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The use of HMAC-SHA256 is RECOMMENDED.
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7. Acknowledgments
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Olafur Gudmundsson kindly helped in the procedure to deprecate the
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MD5 use in TSIG, i.e., the procedure which led to this memo. Alfred
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Hoenes, Peter Koch, Paul Hoffman and Edward Lewis proposed some
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improvements.
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8. References
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Dupont Expires November 9, 2009 [Page 4]
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Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009
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8.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
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Requirement Levels", RFC 2119, BCP 14, March 1997.
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[RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D., and B.
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Wellington, "Secret Key Transaction Authentication for DNS
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(TSIG)", RFC 2845, May 2000.
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[RFC2930] Eastlake, D., "Secret Key Establishment for DNS (TKEY
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RR)", RFC 2930, September 2000.
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[RFC4635] Eastlake, D., "HMAC SHA TSIG Algorithm Identifiers",
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RFC 4635, August 2006.
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8.2. Informative References
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[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
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April 1992.
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[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
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Hashing for Message Authentication", RFC 2104,
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February 1997.
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[RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1
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(SHA1)", RFC 3174, September 2001.
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[RFC3645] Kwan, S., Garg, P., Gilroy, J., Esibov, L., Westhead, J.,
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and R. Hall, "Generic Security Service Algorithm for
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Secret Key Transaction Authentication for DNS (GSS-TSIG)",
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RFC 3645, October 2003.
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[RFC3874] Housley, R., "A 224-bit One-way Hash Function: SHA-224",
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RFC 3874, September 2004.
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[RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
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(SHA and HMAC-SHA)", RFC 4634, July 2006.
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[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
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IANA Considerations Section in RFCs", RFC 5226, BCP 26,
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May 2008.
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Dupont Expires November 9, 2009 [Page 5]
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Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009
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Author's Address
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Francis Dupont
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ISC
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Email: Francis.Dupont@fdupont.fr
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Dupont Expires November 9, 2009 [Page 6]
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