Subject: [dnsext] I-D Action:draft-ietf-dnsext-tsig-md5-deprecated-02.txt

From: [email-masked]
Date: Mon, 27 Apr 2009 09:45:01 -0700 (PDT)

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the DNS Extensions Working Group of the IETF.

	Title           : Deprecation of HMAC-MD5 in DNS TSIG and TKEY Resource Records
	Author(s)       : F. Dupont
	Filename        : draft-ietf-dnsext-tsig-md5-deprecated-02.txt
	Pages           : 6
	Date            : 2009-04-27

The main goal of this document is to deprecate the use of HMAC-MD5 as
an algorithm for the TSIG (secret key transaction authentication)
resource record in the DNS (domain name system).

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-dnsext-tsig-md5-deprecated-02.txt

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

Below is the data which will enable a MIME compliant mail reader
implementation to automatically retrieve the ASCII version of the
Internet-Draft.

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From: Edward Lewis <[email-masked]>
Date: Mon, 27 Apr 2009 16:34:39 -0400

>      Deprecation of HMAC-MD5 in DNS TSIG and TKEY Resource Records
>               draft-ietf-dnsext-tsig-md5-deprecated-02.txt

>Abstract

The purpose of this document is to change the IANA registry for TSIG
Algorithm Names to deprecate the use of HMAC-MD5 as working keyed hash
algorithm for the TSIG and TKEY methods of providing DNS message
integrity protection.

>
>1.  Introduction
>
>    The secret key transaction authentication for DNS (TSIG, [RFC2845])
>    was defined with the HMAC-MD5 [RFC2104] cryptographic algorithm.  As
>    the MD5 [RFC1321] security was recognized to be lower than expected,
>    [RFC4635] standardized new TSIG algorithms based on SHA
>    [RFC3174][RFC3874][RFC4634] digests.

"lower than expected" -> this should be reworded.  Also the verb 
tenses I think are off -

    The secret key transaction authentication for DNS (TSIG, [RFC2845])
    has been defined with the HMAC-MD5 [RFC2104] cryptographic algorithm.
    When MD5 [RFC1321] security came to be considered obsolete [reference?],
    [RFC4635] standardized new TSIG Algorithms Names based on SHA
    [RFC3174][RFC3874][RFC4634] digests.

>
>    But [RFC4635] did not deprecate the HMAC-MD5 algorithm.  This
>    document is targeted to complete the process, in details:

"in detail" (drop the 's')"

>    1.  Mark HMAC-MD5.SIG-ALG.REG.INT as optional in the TSIG algorithm
>        name registry managed by the IANA under the IETF Review Policy
>        [RFC5226]

Can we mark it "historic" instead of "optional?"  Or even "deprecated?"

>2.  Implementation Requirements
>
>    The table of section 3 of [RFC4635] is replaced by:
>
>              +-------------------+--------------------------+
>              | Requirement Level | Algorithm Name           |
>              +-------------------+--------------------------+
>              | Optional          | HMAC-MD5.SIG-ALG.REG.INT |

"Deprecated"?

>4.  IANA Consideration
>
>    This document extends the "TSIG Algorithm Names - per [] and
>    [RFC2845]" located at
>    http://www.iana.org/assignments/tsig-algorithm-names by adding a new
>    column to the registry "Compliance Requirement".
>
>    The registry should contain the following:
>
>     +--------------------------+------------------------+-------------+
>     | Algorithm Name           | Compliance Requirement | Reference   |
>     +--------------------------+------------------------+-------------+
>     | gss-tsig                 | Optional               | [RFC3645]   |
>     | HMAC-MD5.SIG-ALG.REG.INT | Optional               | [][RFC2845] |

Deprecated/Historic?

>5.  Availability Considerations
>
>    MD5 is no more universally available and its use should lead to
>    increasing operation issues.  SHA1 is likely to suffer from the same
>    kind of problem.  To summary MD5 has reached end-of-life and SHA1
>    follows few years behind.

Do you mean "MD5 is no longer universally available"?

And SHA1 "is [eventually?} likely to suffer" - any time soon?  This 
doc title is about HMAC-MD5, not SHA1.

>6.  Security Considerations
>
>    This document does not assume anything about the cryptographic
>    security of different hash algorithms.  It is a routine maintenance,
>    its goal is better availability of some security mechanisms in a
>    predictable future.

That's okay for HMAC-MD5 if there is a reference to a statement it is 
obsolete, but not so for SHA1 (yet).  I'd drop any change to SHA1 for 
now and add pointers to HMAC analysis to support this assertion.

-- 
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Edward Lewis
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---

From: Francis Dupont <[email-masked]>
Date: Thu, 30 Apr 2009 00:07:27 +0200

In your previous mail you wrote:

=> this draft addresses all issues raised, I ask for WGLC...

Thanks

[email-masked]

   	Title           : Deprecation of HMAC-MD5 in DNS TSIG and TKEY Resource Reco
  rds
   	Author(s)       : F. Dupont
   	Filename        : draft-ietf-dnsext-tsig-md5-deprecated-02.txt
   	Pages           : 6
   	Date            : 2009-04-27