phc-discussions - Re: [PHC] Argon2 improvement thread

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Date: Tue, 21 Jul 2015 21:45:18 +0200
From: Solar Designer <solar@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Argon2 improvement thread

On Tue, Jul 21, 2015 at 12:24:00PM -0700, Bill Cox wrote:
> If Alexander proposed to integrate his PWXFORM (I don't know what MAXFORM
> is), then I would be for it.  This would satisfy my request for improved
> GPU resistance, and also my request for multiplication-chain computation
> time hardening.

MAXFORM is the scalar equivalent to (and subset of) pwxform.  It's
neither parallel, nor wide, but is otherwise the same.

It would co-exist with Argon2's existing SIMD code.

> There are only two really outstanding SIMD-optimized mixing functions which
> were used in this competition, IMO.  The choices are the reduced-Blake2
> with or without it's multiplication modification, and PWXFORM.  I suspect
> between Samuel Neves, Alexander, and the Argon2 team, they could figure out
> the best solution.

Switching Argon2 to use pwxform would be too much of a change - not
code-wise, but design-wise.  If we were to do that, then it'd be better
to go with (simplified) yescrypt or the like instead, which we already
have separately (just not as the PHC winner).

Alexander