phc-discussions - Re: [PHC] Testing Password Hashing functions

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Message-ID: <1365177206.2493.10.camel@test.quest-ce.net>
Date: Fri, 05 Apr 2013 17:53:26 +0200
From: Yann Droneaud <ydroneaud@...eya.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Testing Password Hashing functions

Hi,

Le vendredi 05 avril 2013 à 10:48 +0000, Poul-Henning Kamp a écrit :
> In message <1365158596.26812.18.camel@...t.quest-ce.net>, Yann Droneaud writes:
> 
> >For hashing functions, especially cryptographic hashing functions,
> >what are the tools to test them ?
> 
> A good starting point is to treat it as a PRNG:  A hash function
> whould have the exact same mathematical properties as a PRNG, with
> the single addition that the same input always produces the same
> output.
> 

I would rather say that a hash function could be used to built a PRNG
(basically either hashing its previous output value or hashing the
output from a validated (P)RNG) then this PRNG could be evaluated.

A PRNG has only its seed as input and produces an infinite amount of
output values, while the hash function has one input value and one
output value.

A hash function has other properties to be evaluated regarding its
output (avalanche effect, etc.)

So using the PRNG test is probably a first evaluation step, but doesn't
seems to be enough.

IANACNAM (I am not a Cryptographer nor a Mathematician)

So what others tools, methods are going to be used to evaluate password
hash functions ?

Regards.

-- 
Yann Droneaud
OPTEYA