Re: [TLS] Consensus Call: FNV vs SHA1

Simon Josefsson <simon@josefsson.org> Tue, 11 May 2010 16:19 UTC

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From: Simon Josefsson <simon@josefsson.org>
To: Nicolas Williams <Nicolas.Williams@oracle.com>
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Date: Tue, 11 May 2010 18:19:28 +0200
In-Reply-To: <20100511160434.GK9429@oracle.com> (Nicolas Williams's message of "Tue, 11 May 2010 11:04:35 -0500")
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Cc: tls@ietf.org
Subject: Re: [TLS] Consensus Call: FNV vs SHA1
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Nicolas Williams <Nicolas.Williams@oracle.com> writes:

> On Mon, May 10, 2010 at 10:39:28AM -0700, Joseph Salowey (jsalowey) wrote:
>> I don't see much new being added to this discussion at this point.  I'd
>> like to close on this.  If you have an opinion please indicate if:
>> 
>> a) You favor SHA-1
>> b) You favor FNV-1a
>
> Subsequent discussion shows that hash collisions are a problem for this
> protocol, though not a security problem.  As such I believe that (b) is
> now out of order, and therefore I now favor (a), with less or no
> truncation.

I'd like to see the document nail down what properties is required from
the digest, and explain the hash collision problem.  If hash collisions
really is a problem, that prompts the old question if we need hash
agility after all.  It isn't clear to me that moving from FNV-1a to
SHA-1 actually improves anything wrt collisions.

/Simon