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Date: Tue, 4 Dec 2012 10:45:09 +0530
From: Sayantan Datta <>
Subject: Re: bitslice DES on GPU

On Fri, Oct 19, 2012 at 2:01 AM, Solar Designer <> wrote:

> > Since the 96 index array is almost constant the indexing could be
> > done prior to execution. However it might require some radical approach
> > like pre compiling the kernels manually.
> Yes, or patching binary kernels at runtime.  This is something I had in
> mind before we started.  I previously tested this on CPU, for a 7%
> speedup over what we currently have in JtR.  On GPU, the speedup will
> likely be much greater.  You may measure it by temporarily (in a copy of
> the code) eliminating E[] and hard-coding the indices for a certain salt
> value (it is easiest to do this for salt=0 - just take the indices out
> of the LM hash code and use the test hash with ".." for the salt).
> Alexander

Did that. Performance increased from 67M to 110M using the zeroed salt with
2501 iterations on 7970.

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