phc-discussions - Re: [PHC] Another PHC candidates "mechanical" tests (ROUND2)

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Date: Tue, 31 Mar 2015 13:24:47 +0200
From: Krisztián Pintér <pinterkr@...il.com>
To: "discussions@...sword-hashing.net" <discussions@...sword-hashing.net>
Subject: Re: [PHC] Another PHC candidates "mechanical" tests (ROUND2)

On Tue, Mar 31, 2015 at 5:11 AM, Hongjun Wu <wuhongjun@...il.com> wrote:
> Eventually it turns out that a number of second round candidates need to cut
> the round number significantly.   I feel that it is no longer true that
> those PHC candidates are based on strong crypto primitives, although they
> are still very strong.

it depends on the primitive. for example reduced round keccak is shown
to be safe in certain modes, and i would claim that password hashing
is such a mode. namely authors explored the use of reduced round
keccak-f in keyed modes, in which an attacker is not in control of the
input. the conclusion was that round numbers down to 3 from 24 are
still considered safe.

http://keccak.noekeon.org/KeccakDIAC2012.pdf
4.1 The donkeySponge construction

i assume we can say in general that primitives designed to deal with
malicious input are overly strong for password hashing, and in some
cases, it can actually be shown.