[Cfrg] Comments on draft-mattsson-cfrg-det-sigs-with-noise-02

Jim Schaad <ietf@augustcellars.com> Fri, 01 May 2020 03:14 UTC

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From: Jim Schaad <ietf@augustcellars.com>
To: <draft-mattsson-cfrg-det-sigs-with-noise@ietf.org>
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Date: Thu, 30 Apr 2020 20:14:04 -0700
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Subject: [Cfrg] Comments on draft-mattsson-cfrg-det-sigs-with-noise-02
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*  Section 1 should note the fact that these updates are invisible to the
validator of the signature.

* Section 3  Is there any advantage to stealing one of the zeros from the
end padding and using it to pad between  'Z' and 'x' in the construction?  I
would assume that it should use the '0'/'1' construction between steps d and
f.

* Section 3 - is there any advantage to padding with 0x01 in step f rather
than 0x00?

* Section 4 - it would be good to give a hint about why the construction in
randomness-improvements is not recommended.  I can make some guesses, but
that does not help me in evaluating a different PRNG.

* Section 5 - I would be strongly in favor of replacing HMAC with KMAC when
SHAKE algorithms are used.

* Section 6.1 - Given that you recommended against the use of
randomness-improvements, I don't see why this would be a normative
reference.

Jim