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Message-ID: <20131121033745.GD30964@openwall.com>
Date: Thu, 21 Nov 2013 07:37:45 +0400
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: Questions and suggestions to build a home cracking box. :)
On Wed, Nov 20, 2013 at 08:24:26AM -0600, Richard Miles wrote:
> I tried OMP before but it was not very stable, sometimes it worked,
> sometimes not, so I would like to avoid it, except if it's stable now. :)
This is news to me, unless you were on Windows and used other than one
of our own builds. Can you describe those stability issues, please? -
including what version/build of JtR you were using and the OS you were on.
OpenMP is usually not the most efficient way to parallelize JtR, but it
is stable, with the only known exception being that Cygwin shortcoming
(patched in the version of cygwin1.dll that we're distributing with JtR).
> Between OMP and Fork what is faster?
In terms of c/s rate, --fork is faster. For slow hashes, --fork is a
bit faster. For fast hashes, --fork is a lot faster.
In terms of passwords cracked per second, it depends. OpenMP uses just
one stream of candidate passwords, which JtR tries to keep in an optimal
order. --fork uses multiple streams, so the order in which candidate
passwords are tested may be (slightly) less optimal. In fact, in some
cases some of the child processes may terminate significantly sooner
than others.
Overall, I recommend --fork, but if its drawbacks start to annoy you and
you're attacking a slow hash type, you may use OpenMP for a more
pleasant experience (other than on Windows with buggy Cygwin), at the
expense of slightly lower c/s rate (e.g., on a certain machine md5crypt
with OpenMP is 215k c/s, with --fork 225k c/s combined for 8 processes).
> Both support all password hashes
> available on your github (https://github.com/magnumripper/JohnTheRipper)?
No. OpenMP support is included for a subset of hash types only. --fork
is supported for all (in bleeding-jumbo branch).
Alexander
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