phc-discussions - Re: [PHC] BSTY - yescrypt-based cryptocoin

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Message-ID: <541304E5.3050905@ciphershed.org>
Date: Fri, 12 Sep 2014 10:36:21 -0400
From: Bill Cox <waywardgeek@...hershed.org>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] BSTY - yescrypt-based cryptocoin

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On 09/11/2014 03:24 AM, Solar Designer wrote:
> Also interesting is what happens with 1 MiB per hash:
> 
> 6 rounds, 4 threads: 6300 6 rounds, 8 threads: 7300 2 rounds, 4 
> threads: 13400 2 rounds, 8 threads: 14550 to 15400 (unstable 
> speed)
> 
> As expected, this makes 8 threads the optimal choice again.  The 
> speed and bandwidth usage difference between 6 and 2 rounds 
> improves to 2x+. Of course, like before this is countered by the
> 3x reduction in compute hardening per hash computed (so up to 1.5x 
> overall).
> 
> When AVX2 code is written, it will improve speeds at 6 rounds 
> slightly (but less so at 2 rounds).
> 
> Alexander
> 

I think I prefer the 2 round vs 6 round for this PoW application.
Designing fast multipliers is hard, but so is designing 2MiB fast
SRAMs.  Doubling the SRAM bandwidth and cutting the computation speed
by 3X seems like a reasonable trade-off to me, especially since you
also gain speed in block chain verification.

I might be tempted to increase to 4MiB though :-)

Here's one problem I have with GlobalBoost-Y.  It sounds like a dream
come true for botnet operators.  Can you think of anything to defend
against botnet GlobalBoost-Y mining?

Bill
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