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Date: Sat, 7 Jul 2012 13:48:08 +0400
From: Solar Designer <>
Subject: Re: optimized mscash2-opencl

On Sat, Jul 07, 2012 at 01:31:06PM +0400, Solar Designer wrote:
> Actual run:
> $ ./john -i=alpha ~/john/contest-2011/hashes-all.txt-1.mscash2 -fo=mscash2-opencl -pla=1

I let this run until:

guesses: 67  time: 0:00:28:24 0.00%  c/s: 102413  trying: bara - choedia
Use the "--show" option to display all of the cracked passwords reliably
Session aborted

Somehow john.pot and john.log were not being updated during the run,
even though they should have been updated every 10 minutes.  They were
updated a few seconds after I sent the process a SIGHUP.  They were also
updated when I pressed ^C.  Surprisingly, the process terminated
cleanly.  I am more used to seeing:

../../../thread/semaphore.cpp:87: sem_wait() failed

on ^C, with nothing saved, when using AMD's OpenCL. :-(  However, like I
said, this time everything worked just fine in this respect.

I validated the cracked 67 passwords with the CPU --format=mscash2 - all
of them got re-cracked just fine.  So we did not get any false positives.

I did not check for possible false negatives.  Someone will need to run
the test suite.

Also notice how we stayed within the same "bara - choedia" set of
candidate passwords for half an hour.  It'd take roughly:

262144*1090/102413 = 2790 seconds

to advance any further.

Maybe max_keys_per_crypt is too high for convenient use.  We could want
to try reducing it and see if we're able to keep the speed almost as high.


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