phc-discussions - Re: [PHC] Specification of a modular crypt format

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Message-ID: <560BD7B2.408@openwall.com>
Date: Wed, 30 Sep 2015 15:38:10 +0300
From: Alexander Cherepanov <ch3root@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Specification of a modular crypt format

On 2015-09-28 14:50, Dmitry Khovratovich wrote:
> On Sun, Sep 27, 2015 at 11:20 PM, Alexander Cherepanov <ch3root@...nwall.com> wrote:
>> Hm, there seems to be some indeterminism in Argon2 itself here? According
>> to spec: "The actual number of blocks is $m'$, which is $m$ rounded down to
>> the nearest multiple of $4p$."
>
>   To ease the hashing process, Argon2 allocates the same amount of memory
> for each thread. Therefore, when you request 9 or 10 KB of memory and 2
> threads, 8 KBytes will be used in fact. The output values will be
> different, of course, as the requested 'm' is hashed as well.

Great!

And about parallelism. It seems it's now allowed to be up to 255 but one 
place in the spec is not updated: "Parallelism. Argon2 may use up to 64 
threads in parallel, although in our experiments 8 threads already 
exhaust the available bandwidth and computing power of the machine."

-- 
Alexander Cherepanov