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Re: [ietf-dkim] agenda item on upgrading hash algorithms?

2006-02-24 14:04:44

----- Original Message -----
From: "Hallam-Baker, Phillip" <pbaker(_at_)verisign(_dot_)com>
To: "John R Levine" <johnl(_at_)iecc(_dot_)com>; "Eliot Lear" 
<lear(_at_)cisco(_dot_)com>
Cc: <ietf-dkim(_at_)mipassoc(_dot_)org>
Sent: Friday, February 24, 2006 2:52 PM
Subject: RE: [ietf-dkim] agenda item on upgrading hash algorithms?


The reason people are pushing for SHA-256 now is not because there is a
probable imminent break. It is because we know just how long the process
of switching algorithms takes.

I agree.

I think that the consenus here is to:

1) Start the SHA-256 transition now, making it a MUST for verifiers,
MUST/SHOULD for signers.

My only take here is that this MUST/SHOULD for signers will always be tagged
with a basic implementation question of

   "well, which one should I use?"

So I think it should be carefully phrase to say:

    SIGNERS "SHOULD" use the highest form of security first among the
    choices currently available {SHA-1, SHA-256}.  Although it is out
    of the scope of this specification, an SIGNER "MAY" use a
    VERIFIER lookup concept to determine the highest form of
    security it offers.

This helps or resolves both issues and addresses the future, especially the
case if indeed when a method is hacked and DKIM signer wishes to quickly
migrate to a new method as supported by the validators. In my view, it is
almost inevitiable, the signer will need to be a lot smarter than the
documentation calls for. i.e. find out more about the host system it is
about to send a "valuable" mail to.

--
Hector Santos, Santronics Software, Inc.
http://www.santronics.com






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