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Date: Thu, 24 May 2012 23:07:12 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Timing issues
When I tried the high-rounds crypt-SHA512 hash (as seen on john-users)
on bull just now, I stumbled onto two issues, not really new to me but I
think they need to be looked at.
1. I tested using --max-time=60 but it was not obeyed. This option is
designed so that if the self-test takes 40 seconds the expected total
run time would be about 1:40 instead of 60 seconds, but this does not
explain it (it ran for several minutes before I killed it). I will look
into this later but I have a feeling it's something with our OS_TIMER=0
- does that make sense? I have seen other weird things that started to
happen after we did this change (can't remember exactly what right now,
I think it was something like "reported time not reflecting wall time").
2. When cracking (as opposed to benchmarking) the time before cracking
actually starts is counted:
guesses: 0/7680 time: 0:00:00:43 c/s: 175 trying: HC - ��
guesses: 0/76800 time: 0:00:01:00 c/s: 1279 trying: W� - �>
guesses: 0/176640 time: 0:00:01:23 c/s: 2119 trying: #Z� - #��
The real speed is constantly at something like 4300 c/s considering it
did not even start until about 0:40. This makes quick tests like this
one hard to do (need to run a lot longer, or re-calculate manually which
is what I did, hopefully not totally wrong). Do we want to change this?
It could be considered cheating in a way but I think the current
behaviour is just confusing (say for example you try to follow the
suggested homing for markov mode - you will end up with a too low level,
and stop long before your targeted runtime)
This would of course be mitigated a little by fixing the underlying
issue that the self-test takes 40 seconds.
magnum
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