Subject: Re: Last Call: 'Email Submission Between Independent Networks' to BCP

From: Sam Hartman <[email-masked]>
Date: Sun, 03 Jul 2005 21:54:07 -0400

>>>>> "Simon" == Simon Josefsson <[email-masked]> writes:

    Simon> "Kurt D. Zeilenga" <[email-masked]> writes:
    >> It is my recommendation that the mandatory-to-implement
    >> "strong" authentication mechanism for this protocol be either:
    >> DIGEST-MD5 (with a mandate that implementations support its
    >> data security layers) TLS+PLAIN (with a recommendation that
    >> PLAIN not be used when TLS is not in use).

    Simon> I don't think recommending the DIGEST-MD5 security layers
    Simon> is a good idea.

    Simon> The integrity layer is hard coded to be HMAC-MD5, with keys
    Simon> derived using a home-grown key-derivation function based on
    Simon> MD5.

I think the key derivation function used by digest-md5 is sound given
reasonable assumptions.  I am reasonably certain this is true under
the random oracle assumption but believe it may be true under weaker
assumptions.

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