phc-discussions - Re: [PHC] friendly warning about randomness tests

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Message-ID: <5404EA1E.8010205@ciphershed.org>
Date: Mon, 01 Sep 2014 17:50:22 -0400
From: Bill Cox <waywardgeek@...hershed.org>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] friendly warning about randomness tests

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On 09/01/2014 04:59 PM, Krisztián Pintér wrote:
> 
> the diehard, testu01, dieharder, etc test suites are not
> cryptographic tools. failing these tests is a clear break, and at
> least calls for another postprocessing step (together with an
> assessment of actual entropy content of the raw output). however,
> passing such tests mean exactly nothing in crypto context.
> 

Agreed.  Failing the tests means you have a problem.  Passing them
does not mean your hash function is secure.  POMELO had failed earlier
when it had a bug, so that's why I reran it.

So, take your 32-bit MT SRNG.  Now, generate data from it 7 times with
different random seeds, and do a non-linear combination of them (if
the last operator in the MT function was an ADD, do and XOR or
vise-versa).  This is closer to what I'm seeing in POMELO.

Bill
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