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Date: Wed, 13 Jun 2012 22:02:21 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: bf-opencl

Sayantan -

I've just tried running bf-opencl in magnum-jumbo on HD 7970 against
pw-fake-unix from:

http://openwall.info/wiki/john/sample-hashes

This triggered an ASIC hang on the 7970 after a few minutes.  Also, only
one password was cracked:

$ ./john -fo=bf-opencl ~/john/pw-fake-unix -w=password.lst -pla=1
OpenCL platform 1: AMD Accelerated Parallel Processing, 2 device(s).
Using device 0: Tahiti
*****See 'opencl_bf_std.h' for device specific optimizations******
Loaded 3107 password hashes with 3107 different salts (OpenBSD Blowfish OpenCL [BF_OPENCL])
Suppressed 1 duplicate lines.
omega            (u2461-bf)
guesses: 1  time: 0:00:00:14 0.00%  c/s: 233  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:21 0.00%  c/s: 457  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:25 0.00%  c/s: 519  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:29 0.00%  c/s: 565  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:33 0.00%  c/s: 601  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:37 0.00%  c/s: 629  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:40 0.00%  c/s: 652  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:44 0.00%  c/s: 671  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:48 0.00%  c/s: 687  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:52 0.00%  c/s: 701  trying: 123456 - jethrotull
guesses: 1  time: 0:00:00:55 0.00%  c/s: 713  trying: 123456 - jethrotull
guesses: 1  time: 0:00:01:33 0.00%  c/s: 779  trying: 123456 - jethrotull
guesses: 1  time: 0:00:01:49 0.00%  c/s: 793  trying: 123456 - jethrotull

Somehow the c/s rate starts low and increases slowly.  I don't have a
good explanation for this in this case.  The benchmark had reported
something like 2500 c/s.

Running on GTX 570 cracked only this same omega password (I interrupted
after a minute or so).

I realize that matching 3000 plaintexts against 3000 hashes (each with
its own salt) at this low c/s rate is very time-consuming, and is a bit
more time-consuming when keys_per_crypt is large, but I think we should
be seeing many more passwords cracked during 2 minutes.  Each
crypt_all() call should result in about 1 password cracked, and it
should be taking about 4 seconds (at 800 c/s).  So we should have seen
about 25 passwords cracked above, not one.  I think there's a bug.

Alexander

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