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Date: Mon, 27 May 2013 00:48:58 +0400
From: Solar Designer <>
Subject: Re: Parallella: bcrypt

On Sun, May 26, 2013 at 09:38:00PM +0200, Katja Malvoni wrote:
> ORIGINAL with *-O2*
>       Message from eCore 0x88a ( 2, 2): Result:
> "$2a$05$XXXXXXXXXXXXXXXXXXXXXOAcXxm9kjPGEMsLznoKqmqw7tc8WCx4a"#
>       Execution time - Epiphany: 42.688000 ms

OK, this is slightly better, but still 4x slower than our target speed.
A 2x difference is explained by non-use of the integer instructions on
the FPU (of those, perhaps we'd be able to use just IADD, though).

A further 2x difference is mostly not explained... we'd need to take a
look at the code, or maybe we need to try inter-mixing two instances of
bcrypt first, as it helps to hide instruction latencies.

A minor optimization you'd need to make is compute only the first 64
bits of output (one Blowfish block size) on Epiphany.  When these happen
to match the first 64 bits of a bcrypt hash loaded for cracking (which is
likely to happen only if we have attempted the correct password), JtR
will compute the full hash on host CPU in cmp_exact() (just to make sure
we do indeed have the correct password and the hash loaded for cracking
had not been corrupted).  This will provide very little speedup, though.

Anyhow, your immediate next task is making use of all cores.  Even at
only 23 c/s per core as above, 16 cores will do ~370 c/s, which is the
speed of a Pentium 4 (but at a much lower power consumption), although
new multi-core x86 CPUs are roughly 10x faster.  Indeed, 370 c/s at
$2a$05 is not a serious speed for actual use currently, but we're merely
experimenting with this new technology.  Hopefully, we'll be able to
improve the speed to up to 1600 c/s on 16 Epiphany cores, and hopefully
we'll have 64-core and larger Epiphany chips later.



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