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Date: Sun, 10 Feb 2013 02:57:05 +0400
From: Solar Designer <>
Subject: cracking partial/inexact hashes (was: Support for PBKDF2 (SHA512))

I am moving this to john-dev.

On Sat, Feb 09, 2013 at 11:45:29PM +0100, magnum wrote:
> I could not resist implementing a proper cmp_all() just to verify that the 1024 bit OSX hashes were indeed longer PBKDF2 output. They are. This is pretty silly considering that you don't have to calculate more than the first 512-bit block for knowing you have cracked the right password. We do it now anyway just for good measure, and because we can do it without slowing things down. With a totally na??ve approach, those hashes would take twice as long to calculate.

Maybe we should print a warning when the first 512 bits match, but
further data does not?  This would indicate data corruption/typo in the
extra data.

In fact, we could do that for less than 512 bits (e.g. 128?) and in
other formats as well.  In general, a partial/inexact hash cracking
capability would be somewhat useful.  e.g. the AIX ssha512 hash for
"colorado" has one character unknown (it's shown as a space on the web
page, IIRC) - yet we should be able to crack it with the right algorithm.


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