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Date: Thu, 29 Mar 2012 04:07:05 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: JtR: GPU for slow hashes

On Wed, Mar 28, 2012 at 11:21:50PM +0530, SAYANTAN DATTA wrote:
> On Wed, Mar 28, 2012 at 5:54 PM, SAYANTAN DATTA <std2048@...il.com> wrote:
> >   Here are a few problems I'm facing.Since ATI 4000 series gpus don't
> > support byte_addressable_store I have to work around this problem by using
> > only uint as the data type for temporary data storage.This problem exsist
> > with many of the hash algorithms already implemented with openCL eg MD5,4
> > etc.However ATI 5000 series and above seems to support
> >  byte_addressable_store.So the exsisting codes should work fine on 5000 or
> > above GPUs but for 4000 series or below they need to be reimplemented.The
> > workaround is also causing some performance penalties.
...
>   Since my GPU dosen't support byte_addressable_store it is becoming an
> increasingly uphill task to implement the HMAC_SHA1 algorithm.Using the
> uint[]  instead of uchar[] is a probable solution but debugging the
> code becomes very much time consuming.
>    I  have also considered using 4 uchar16 vectors to  replace single
> uchar[64] array but it is resulting in too much branching in the code.If
> you have any suggestion please let me know.

I am totally unfamiliar with this - maybe someone else will comment.
Lukas, Milen, Samuele, Claudio, magnum - maybe some of you?

It is not necessarily a bad thing that the task turned out to be more
complicated - you have a better chance to demonstrate your ability to
work on complex tasks in this way. ;-)

Thanks,

Alexander

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