Date: Thu, 22 Dec 2011 17:21:51 +0530 From: piyush mittal <piyush.cse29@...il.com> To: john-dev@...ts.openwall.com Subject: Re: Bit slice implementation of DES based hashes Hello, Sorry for replying too late. I was busy in some urgent work. Each bit of what? > Each bit of processor is what I am talking of,like in 64 bit processor each 64 bit will behave as different processor. According to Eli Biham's paper,In Des Bitslice implementation he considered processor as a SIMD computer,ie as 64 parallel one bit processor computing the same instruction. "To further increase the speed"? Would there be any speed increase at > all (compared to a non-bitslice implementation) without this? And what > alternative(s) did we have? > > Yes.Speed has been increased,like in his paper he told: In DES, the input of each S box depends only on the output of only six S boxes in the previous round. Thus, the code can be optimised to start computing the next round while still computing the preceding one. This can speed up implementations on pipelined processors, where we can compute several instances in parallel. These two are not valid answers to my questions. > Truly speaking I am not getting how B and K is being initialised in JTR code according to the architecture of processor specified.And if I will be able to get it then i can also complete my conversions.However I read its corresponding header file but then also I am not getting.Even I tried to take some idea from DES_bs_get_hash() function where we are fetching hash from B but I am not getting what "B DEPTH" represents and why we have taken b to b. I am sorry for asking those questions like that, but I think that you're > missing some of the basics and I am trying to get you to realize what > exactly you're missing and learn that. > No need to say sorry because in this way I can learn only.And yes its true that I am missing some basic things as I explained you above. Thanking You On Tue, Dec 20, 2011 at 9:34 PM, Solar Designer <solar@...nwall.com> wrote: > On Tue, Dec 20, 2011 at 05:56:15PM +0530, piyush mittal wrote: > > > > > > Can you please describe what bitslicing is, in your own words? > > > > In Bitslicing ,all combination of bits operates simultaneously and > > parallelly i.e each bit will behave as a different processor. > > Each bit of what? > > > The same > > concept we are using here in DES.Like in 64 bit machine 64 plain text's > > encryption can be done simultaneously and parrallely. > > OK. > > > However here we have > > used non standard implementation of DES i.e structure of DES is broken > down > > into AND,OR NOR.. gates to further increase the speed. > > "To further increase the speed"? Would there be any speed increase at > all (compared to a non-bitslice implementation) without this? And what > alternative(s) did we have? > > > > What portion(s) of the DES block(s) does each element of B hold? > > > > > > What portion(s) of the DES key(s) does each element of K hold? > > > > 64 elements of block is holded by each element of B > > 56 elements of block is holded by each element of K > > These two are not valid answers to my questions. Here are some > ridiculous questions in line with your answers above: > > What is an "element" of a block? > > Are you implying that one element of B has a different size than one > element of K (64 "elements" in it vs. 56 "elements")? Is this > discrepancy also seen in the data types used in the program? If not, > what does that mean? > > I am sorry for asking those questions like that, but I think that you're > missing some of the basics and I am trying to get you to realize what > exactly you're missing and learn that. > > > Now I am starting NETLM_fmt.c and Oracle code I will also give you after > it. > > Now I will not inquire further questions to you. > > OK, that's your choice. > > Alexander > -- Piyush Mittal Department of Computer Science and Engineering National Institute of Technology,Rourkela INDIA Content of type "text/html" skipped
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