Date: Tue, 27 Mar 2012 21:09:15 +0530 From: SAYANTAN DATTA <std2048@...il.com> To: john-dev@...ts.openwall.com Subject: Re: JtR: GPU for slow hashes On Tue, Mar 27, 2012 at 8:08 PM, Solar Designer <solar@...nwall.com> wrote: > On Tue, Mar 27, 2012 at 05:21:44PM +0530, SAYANTAN DATTA wrote: > > I have a basic question regarding MSCash2. > > BTW, you probably already found these, but in case not: > > http://openwall.info/wiki/john/MSCash2_simple_code > http://openwall.info/wiki/john/MSCash2 > > These are a couple of implementations/descriptions of MSCash2 written by > contributors to JtR. These may be easier to understand than code > currently in JtR is. > > > In above algorithm two inputs namely ussrname and password are used to > > produce a certain hash.Then the generated hash is compared with the > stored > > value and if they are equal then the username and password entered are > > correct.Now we hit and try different values of password to produce a hash > > which matches the given value .So does this mean the username is some > fixed > > string?? > > For one hash being cracked, yes. > > > i.e is the username known to us beforehand and we only have to > > guess the password? > > Yes. > > > Right now my code assumes the username a fixed string.Is it all right?? > > Maybe not, depending on what you mean by assuming a fixed string - > compile time constant vs. runtime value fixed only for a given hash > currently being processed (out of many loaded for cracking). > > JtR supports cracking of many hashes at once, which may correspond to > different usernames. In MSCash2, the usernames are effectively used as > salts - so JtR formats' interfaces for salts are used to support them. > You also need to support running with an arbitrary set of salts > (usernames) and hashes loaded for cracking at once (e.g., there might be > 10000 hashes with 9900 different salts). > > Also note that you only need to implement the PBKDF2 step on GPU - the > rest may stay on CPU. Lukas did the same in his CUDA code (based on my > suggestion). This may simplify the task, and it will let us easily > reuse the PBKDF2 with SHA-1 implementation for things such as WPA. > > Alexander > > > hi, Yeah I mean runtime value fixed only for a given hash being processed. And thank you for the suggestion. -Sayantan Content of type "text/html" skipped
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