Subject: [TLS] P_hash / PRF confusion

From: Mike <[email-masked]>
Date: Sat, 24 May 2008 13:33:28 -0700

There is a confusing aspect to the definitions of P_hash and
the PRF that should probably be addressed.  The problem is
that "seed" is used in both definitions, but they are not
the same value:

P_hash(secret, seed) = HMAC_hash(secret, A(1) + seed) +
                        HMAC_hash(secret, A(2) + seed) +
                        HMAC_hash(secret, A(3) + seed) + ...

PRF(secret, label, seed) = P_<hash>(secret, label + seed)

Someone could easily make the mistake that the seeds are the
same and leave the label out of the P_hash computation.  I
think an easy solution to this problem is to simply rename
one or the other seeds.

Mike
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From: Eric Rescorla <[email-masked]>
Date: Sat, 24 May 2008 17:48:11 -0700

At Sat, 24 May 2008 13:33:28 -0700,
> think an easy solution to this problem is to simply rename

This has been there since TLS 1.0. Given that we're in
AUTH48, I don't think this is a critical enough change
to be made at this time.

-Ekr

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