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Date: Sat, 24 Mar 2012 05:37:16 +0400
From: Solar Designer <>
Subject: Re: JtR: GPU for slow hashes

On Fri, Mar 23, 2012 at 10:27:09PM +0530, SAYANTAN DATTA wrote:
> ... I want to apply for GSoC 2012 project idea "JtR: GPU for slow hashes  ".
> Therefore ,based on my capabilities is it appropriate to apply for the
> above project.Please reply.

Please feel free to apply, but in order to have a chance to be accepted
you need to demonstrate your ability to produce efficient code - not
just faster than a straightforward implementation on CPU, but on par
with what competing tools achieve on GPU (when a given hash type is also
supported by other GPU-enabled tools) and/or many times faster than what
a nearly optimal SIMD-enabled CPU implementation achieves.  You have to
actually achieve that for at least one hash type before the student
selection deadline (say, by April 15 or so - to give us at least a few
days until the April 20 hard deadline to review and test your code).

As an alternative or additionally to implementing support for a new
hash type (for which we do not have any OpenCL or CUDA code currently),
you may optimize some of the existing code - show that you're able to
identify possible optimizations that the original author missed or did
not have time to implement. ;-)

There are also some hash types for which we have only CUDA or only
OpenCL code - you may implement the other.  However, if you pick a
"fast" hash, then you won't be able to show whether your code is
efficient or not yet (that will require changes to JtR's formats
interface first).  So either do it for a "slow" hash (as you had
intended) or make it not your only task completed by April 15 (but
rather an extra task for bonus points).

You may obtain the current code with:

git clone git://

According to the table at we
currently lack MSCash2 in OpenCL (but we have it in CUDA).  You may
experiment with this one and compare your resulting speed numbers
against hashcat's.  This is just a suggestion; please feel free to pick
something else instead.

Please let us know if you start work on any of this (and on what
exactly), and please post weekly updates (like you would need to under
GSoC, so it's good to start practicing that as well).



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