john-users - JtR/OpenMP against Gawker passwords

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Message-ID: <20101215205217.GA1528@openwall.com>
Date: Wed, 15 Dec 2010 23:52:17 +0300
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Cc: Jon Oberheide <jon@...rheide.org>
Subject: JtR/OpenMP against Gawker passwords

Hi,

Here's a curious blog post by Jon Oberheide:

http://www.duosecurity.com/blog/entry/brief_analysis_of_the_gawker_password_dump

People are actually starting to make use of the OpenMP support/patches
in/for recent versions of John the Ripper.  That's nice.  In this case,
Jon ran JtR on an 8-core Xeon X5460 machine (two CPU chips) doing over
20M c/s at the "many salts" test.  399380 out of 748039 password hashes
got cracked.

Benchmarking: Traditional DES [128/128 BS SSE2-16]... DONE
Many salts: 20465K c/s real, 2562K c/s virtual
Only one salt: 16003K c/s real, 1999K c/s virtual

Apparently, this was with 1.7.6-omp-des-7.  The slightly older
1.7.6-omp-des-4 patch, also available on the wiki, would do slightly
better at "many salts" (relevant for the run against Gawker hashes), but
a lot worse at "only one salt" (irrelevant in this case).

http://openwall.info/wiki/john/patches

It's also curious how the Gawker hashes have only 3844 different salts.
Normally, for this number of hashes all possible salts would be present -
that is, there would be exactly 4096 different salts.  This suggests a
poor random number generator, which in turn suggests that of the 3844
salts some likely correspond to a lot more hashes than some others.  Thus,
a more efficient attack could be mounted on a large subset of the hashes
(but a much smaller subset of the salts) by using the "--salts" option.

Jon - thank you for performing this analysis and making the blog post!
This might be the first blogged actual use of the OpenMP patch, so this
helps to make more people aware of the functionality.

What did you mean by this Twitter comment, though - "Bad JtR, why did
you forget to load up a third of the hashes? Grrrr..."?  Is this some
kind of usability issue for me to address?

Thanks again,

Alexander

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