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Re: [TLS] Last Call: <draft-kanno-tls-camellia-00.txt> (Additionx

Martin Rex <mrex@sap.com> Tue, 08 March 2011 20:50 UTC

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From: Martin Rex <mrex@sap.com>
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To: hovav@cs.ucsd.edu
Date: Tue, 08 Mar 2011 21:51:18 +0100
In-Reply-To: <AANLkTi=2zMBAKcEOP7rVKUcjU4AorKBDqzNa+3hOR6Co@mail.gmail.com> from "Hovav Shacham" at Mar 8, 11 12:19:52 pm
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Subject: Re: [TLS] Last Call: <draft-kanno-tls-camellia-00.txt> (Additionx
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Hovav Shacham wrote:
> 
> PRFs, unlike collision-resistant hashes, are not subject to birthday
> attacks.  This holds true even when they are constructed using using
> components originating in hash functions, as HMAC is.

I'm sorry, I fail to understand your argument.

  5.  HMAC and the Pseudorandom Function
    http://tools.ietf.org/html/rfc5246#section-5

  7.4.9.  Finished
     http://tools.ietf.org/html/rfc5246#section-7.4.9


The PRF when used for the generation of the finished messages
looks sufficiently similar to HMAC (a keyed hash) and is used like HMAC
for integrity protection and authentication.  So to me, it looks
that the recommendation of rfc-2104 section 5 about truncation
should apply here as well.

-Martin

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