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Date: Fri, 21 Sep 2012 23:21:34 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: bitslice DES on GPU

Hi Sayantan,

On Sat, Sep 22, 2012 at 12:31:26AM +0530, Sayantan Datta wrote:
> I was experimenting with DES_BS_EXPAND set to 0 and using different types
> of memory .
> 
> 1. B[] in local memory and K[] in private register space:
> With this combination I'm getting speeds of around 24M c/s on 7970 and 5M
> c/s on 570.
> 
> 2. B[] in private register space and K[] in local memory
> I'm getting 12M c/s on 570 while I couldn't get it working on 7970. Getting
> hash fails every time. Most likely the problem is with referencing B[]
> array in z(p) macro.

That's curious.  Even more interesting would be speed numbers with the
overhead mostly excluded - that is, use this test vector:

	{"..X8NBuQ4l6uQ", ""},

set the iteration count e.g. to 2501 (any odd value should do), and
multiply the reported c/s rate by 100 (if you picked 2501) to get the
descrypt equivalent cracking speed.

As to the overhead, we'll need to deal with it by other means later.

I just did some math, and I think that your 24M with overhead may
correspond to around 65M in the without-overhead test.  Please confirm
or disprove. ;-)

1/(1/39+1/41) = 19.99

1/(1/39+1/60) = 23.64
1/(1/39+1/65) = 24.38

39M is my guess as to the "overhead speed" alone (without crypto), based
on the 19.9M "with overhead" speed you reported and my 41M
without-overhead test.  Assuming that this "with overhead" speed
remained the same, it'd take around 65M without-overhead speed to
reach/exceed 24M reported for overhead+crypto.

Thanks,

Alexander

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