Date: Thu, 19 Jul 2012 21:30:19 +0530 From: Dhiru Kholia <dhiru.kholia@...il.com> To: john-dev@...ts.openwall.com Subject: Re: fast pbkdf2-sha1 OpenCL kernel On Thu, Jul 19, 2012 at 9:15 PM, jfoug <jfoug@....net> wrote: >>On Thurs, July 19, 2012 10:12 AM Dhiru Kholia wrote: >> >>I am looking for a fast pbkdf2-sha1 OpenCL kernel which can handle >>passwords of length 20, salt size 20 and can output key length of 66. >> >>1) Can the wpa-psk kernel work with password size of 20? If not, can it >>be modified to do the same? I need this for ODF kernel. >> >>2) Currently the output of wpa-psk kernel is 32 bytes, can this be >>increased to 64 + 2 (= 66)? I need this for ZIP AES kernel. >> >>Jim, does you pbkdf2 kernel meet these requirements? Can it be modified >>to do so? > > I am not sure exactly what code you are referring to. If it is the code in > http://openwall.info/wiki/john/MSCash2_simple_code then it can easily handle > 20 bytes of salt, and 20 byte of hash. I was referring to http://openwall.info/wiki/john/MSCash2. It does *not* handle salt lengths > 16 and it does *not* handle passwords of length 20. I have tested it. > I am not sure how the algorithm would output 66 bytes of key, from a 32 byte > hash function. If it was SHA512, then yes, 66 bytes, but not sure if pbkdf2 > can give more key bytes than the base crypt type. This is possible. Take a look at derive_key implementation in JtR. void derive_key(const unsigned char pwd, /* the PASSWORD */ unsigned int pwd_len, /* and its length */ const unsigned char salt, /* the SALT and its */ unsigned int salt_len, /* length */ unsigned int iter, /* the number of iterations */ unsigned char key, /* space for the output key */ unsigned int key_len)/* and its required length */ key_len can be anything. I have actually used a value of 34 (output key size) in zip format with no problem. -- Cheers, Dhiru
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