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Re: [TLS] Summarizing identity change discussion so far

Marsh Ray <marsh@extendedsubset.com> Fri, 18 December 2009 06:44 UTC

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Date: Fri, 18 Dec 2009 00:44:29 -0600
From: Marsh Ray <marsh@extendedsubset.com>
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Subject: Re: [TLS] Summarizing identity change discussion so far
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Blumenthal, Uri - 0662 - MITLL wrote:
> My strong conviction is that the fact of non-zero probability to get
> (e.g.) PKIX identity matching wrong - does NOT invalidate the need
> for something more powerful and usable than memcmp.

I don't believe many participants in this discussion are thinking that
memcmp() is sufficient for general identity comparison, only that it
works a useful percentage of the time to suggest it would be useful for
TLS implementations to provide as an option to application code.

> I'm not convinced
> that MD5 collision exploitation justifies restriction of matching to
> memcmp.

I missed the email where MD5 collisions were raised.

Mainly memcmp has the advantage of simplicity in definition. If a TLS
implementer wanted to provide an option to compare with hashes they
should just document that it works that way.

- Marsh

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