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Date: Thu, 6 Dec 2012 17:56:52 +0100
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: bitslice DES on GPU

On 6 Dec, 2012, at 17:38 , Sayantan Datta <std2048@...il.com> wrote:
> I did the following:
> 
> Set up two hard coded kernels with same salt. Bit reversed a constant at only one position in one of the kernel. Using this loop,
> 
>  //kernel 1
> for(i=0; i< binary_size;i++){
>       iptr = binary + i;
>       if(*iptr== 0xf0000000) printf("Found:%d\n",i);
>     }
> //kernel 2
> for(i=0; i< binary_size;i++){
>       iptr = binary + i ;
>       if(*iptr== 0x0000000f ) printf("Found:%d\n",i);
>     }
> 
> where 'iptr' is int pointer , 'binary' is char pointer and 'binary_size' is size in bytes.
> 
> Now comparing the two sets of found locations, I should be able to pinpoint at least one  common location. However it seems that there are no common location between them!! 
> 
> Is this approach OK? 


I know some people "binary patch" AMD kernels for BFI and stuff but I always thought they actually patch IL code in an ELF binary file and then load that. This will of course be a lot faster than actually recompiling so it might be a better alternative (of course vendor dependant, but I think that currently goes for any method).

I bet Milen would know for sure how to proceed.

magnum

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