john-users - Re: DES with OpenMP

Openwall GNU/*/Linux 3.0 - a small security-enhanced Linux distro for servers

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Date: Tue, 31 Jan 2012 03:36:02 +0400
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: DES with OpenMP

On Mon, Jan 30, 2012 at 01:44:35PM +0000, Alex Sicamiotis wrote:
> I was looking now at the john.log, and for openMP 2 threads it was
> 
> 0:00:00:00 - Candidate passwords will be buffered and tried in chunks of 8192
> 
> for openMP 1 thread it was
> 
> 0:00:11:32 - Candidate passwords will be buffered and tried in chunks of 4096
> 
> and for non-openMP it was
> 
> 0:00:11:38 - Candidate passwords will be buffered and tried in chunks of 128
> 
> ...and I remembered what you said about this code difference. So.. supposing this can give, say +200k c/s which I'm seeing between the openmp and non-openmp, where do I tweak the code to test various values?

This is DES_bs_cpt in DES_bs.h, and this setting is only used in OpenMP
builds.  By default it's 32, but you can try any value starting with 1.

BTW, I guess those 11 minutes seen in the log above are wasted counting
and validating your preprocessed rules, which you have a ridiculous
number of (600 million, IIRC).  Originally, this was not an intended use
for the rules, but I guess I'll need to introduce some better support
for that, which would avoid the waste of time at startup.  Would you
trade saving the 11 minutes for lack of a progress indicator maybe (so
that we don't need to count the rules)?

Alexander