Re: [Cfrg] Second RGLC on "AES-GCM-SIV"

Stefano Tessaro <> Sat, 20 January 2018 19:26 UTC

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From: Stefano Tessaro <>
Date: Sat, 20 Jan 2018 11:26:08 -0800
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Subject: Re: [Cfrg] Second RGLC on "AES-GCM-SIV"
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> The reason for this recommendation is that using a fixed nonce is bad, but
> using counters may lead to pairwise collisions between two encryptors, and
> that’s not ideal either.

In addition to this, one of the points highlighted by our multi-user
analysis (linked above) is that there is a great security benefit in
the multi-user/multi-key setting if we can ensure that each particular
nonce value is re-used by a small number of users only. This is of
course true if nonces are chosen with sufficient randomness. (Our
security bounds show how security degrades as nonces are re-used by
more users.) This is particularly important when using 128-bit keys,
less relevant with longer (256 bits) keys.


Stefano Tessaro
Assistant Professor of Computer Science
University of California, Santa Barbara