phc-discussions - Re: [PHC] Low Argon2 performance in L3 cache

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Date: Sat, 5 Sep 2015 03:11:53 +0300
From: Solar Designer <solar@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Low Argon2 performance in L3 cache

Hi Bill,

On Fri, Sep 04, 2015 at 04:51:31PM -0700, Bill Cox wrote:
> Argon2d memory for 1.2ms hash: 2200 KiB
> Serial multiplies: 2200*96 = 211,200
> ASIC attacker speed using 1ns multipliers: 0.211ms
> area-time product: 0.465 s-KiB
> 
> TwoCats memory for 1.2ms hash: 8192 KiB
> Serial multiplies: 526336
> ASIC attacker speed using 1ns multipliers: 0.526ms
> area-time product: 4.31 s-KiB
> 
> It looks like TwoCats will have about 9X improved time-area defense, when
> we take into account the multiplication chains.

What is it that makes Argon2d so much slower?  Is it needing to perform
two BLAKE2b rounds per sub-block, and the intermediate writes to state?

Is memory (de)allocation overhead excluded from the 1.2ms for both of
these?  And no zeroization done either?  At least we need to ensure the
benchmarks are consistent in this respect.

Can you tune Argon2d and TwoCats for same defensive throughput per CPU
chip (with multiple independent concurrent instances), rather than for
same defensive latency, for a comparison like this?

I think it's primarily throughput per chip that matters at memory sizes
and low latencies like this.  It doesn't really matter if it takes 1ms
or 2ms of latency to reach a few MB, but it does matter what memory per
hash you can reach within a given hashes per second budget (e.g. for
5000 per second per chip).

Alexander