Re: [kitten] WGLC on draft-ietf-kitten-aes-cts-hmac-sha2-06

Benjamin Kaduk <kaduk@MIT.EDU> Fri, 17 April 2015 18:35 UTC

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Date: Fri, 17 Apr 2015 14:35:42 -0400 (EDT)
From: Benjamin Kaduk <kaduk@MIT.EDU>
To: Jeffrey Altman <jaltman@secure-endpoints.com>
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Subject: Re: [kitten] WGLC on draft-ietf-kitten-aes-cts-hmac-sha2-06
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Hi Jeffrey,

On Thu, 9 Apr 2015, Jeffrey Altman wrote:

> raised are significant.   Do we have independent review from trusted
> cryptographers?  I'm not one so will not try to review the math.

I don't believe there was explicit "independent cryptographer" review at
the time you wrote this.  ("Does Nico count as a cryptographer?")

That said, this document is basically just taking some well-understood
building blocks and combining them in well-understood ways.  It differs
from the existing AES enctypes in using encrypt-then-mac (now the
~universal consensus of the community), in using newer hash functions
truncated to a longer length, and in the key derivation algorithm.  The
key derivation algorithm it uses, from NIST SP800-108, is quite well
understood.  Oh, and the default PBKDF2 iteration count was increased.

I do not think that there is any sufficiently novel cryptography going on
so as to require additional review.  If you still feel that more review
(e.g., from CFRG) is necessary, please say so, ideally with some rebuttals
to my above argument.

-Ben