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Message-ID: <113ad92ab7a7f9b7666db423807f70aa@smtp.hushmail.com>
Date: Wed, 20 Nov 2013 09:07:29 +0100
From: magnum <john.magnum@...hmail.com>
To: john-users@...ts.openwall.com
Subject: Re: Questions and suggestions to build a home cracking
box. :)
On 2013-11-20 06:47, Richard Miles wrote:
> I will be using exclusively John The Ripper tool, no other tools such as
> hashcat. I will be running Linux (32 or 64 bits?).
You should definitely use 64-bit. The performance is always better and
sometimes significantly so.
> 1) Modern processors contains multiple cores and threads (there are some
> good processors with 4 cores and 2 threads per core = 8 cores). Most of my
> cracking tasks will be exclusively against one single password hash,
> consequently use --fork or spawn multiple process will be useless, correct?
On the contrary, OMP and fork is beneficial even if you attack only one
hash. You can try n passwords at a time instead of just one.
> 2) Is there a reliable way to use jTr with multiple cores and threads at
> the same time to try crack one single password hash? How?
You just use OMP/fork as you'd do with multiple hashes. For OMP there
are no quirks at all. For fork you might see that one process cracks the
hash and the other processes doesn't get to know that - so they keep
trying until manually killed. This will hopefully be addressed some time
in the future.
> a) They clearly state that Radeon cards are much faster. My question is,
> this information is still true recently?
Yes. For graphics or non-integer maths, nvidia might be as good or even
better but for integers and bit shuffling (which is what we need), AMD
always ran in circles around nvidia.
> b) I have heard that Radeons drivers sucks and are very unstable. Is that
> true?
Unfortunately yes. Once you find a driver that doesn't show a bug nor a
performance reduction in any format you need, hold on to it. Once you
try an upgrade you need to test everything carefully. The built-in
self-tests should catch most such problems so worst case is normally a
known problem as opposed to false negatives (shrug) that you may
experience with some of our competitors.
> c) What is JtR actual support for Radeon cards? At the moment and further
> efforts are better Radeon or Nvidia?
JtR-jumbo is supposed to support *any* OpenCL device as long as you have
proper drivers for it, even future ones without a rebuild/upgrade.
Openwall's test rigs include AMD's, nvidias and an intel MIC.
> d) The infamous Radeon 6990 is not produced anymore and the used ones are
> more expensive in comparison with 7970. LOL! There are newer models that
> was unavailable at that time. What do you guys suggest? Should I buy 2
> better GPUs? Or 3 GPUs that are average? Or one single super GPU?
Our multi-GPU support is not as mature as eg. Hashcats so a single fast
GPU is currently better than two slower. I'd go for a R9 290X but its
drivers are apparently very immature as of this writing. I expect that
problem to go away soon with newer drivers.
> f) Finally, based on your suggestion of GPU card, what are the current
> password hash formats supported?
Bleeding-jumbo branch supports the following using OpenCL (though some
of them are much slower than HashCat):
descrypt-opencl, ssha-opencl, nt-opencl, ntlmv2-opencl,
agilekeychain-opencl, bcrypt-opencl, blockchain-opencl,
md5crypt-opencl, sha256crypt-opencl, sha512crypt-opencl, dmg-opencl,
encfs-opencl, gpg-opencl, keychain-opencl, keyring-opencl,
krb5pa-md5-opencl, krb5pa-sha1-opencl, mscash2-opencl,
mysql-sha1-opencl, ODF-opencl, ODF-AES-opencl, office2007-opencl,
office2010-opencl, office2013-opencl, phpass-opencl, pwsafe-opencl,
rar-opencl, Raw-MD4-opencl, Raw-MD5-opencl, Raw-SHA1-opencl,
Raw-SHA256-opencl, Raw-SHA512-opencl, Raw-SHA512-ng-opencl,
strip-opencl, sxc-opencl, wpapsk-opencl, XSHA512-opencl,
XSHA512-ng-opencl, PBKDF2-HMAC-SHA256-opencl, RAKP-opencl
> 4) Once using GPU for cracking with jTr is it possible to use with
> incremental mode?
>
> 5) Once using GPU for cracking with jTr is it possible to use with
> markov mode?
All cracking modes are supported but for very fast hashes it's not as
fast as it could be. Sometimes it's in the order of 100x slower than
oclHashcat. Fixing that is WIP but currently that work seem to have
stalled completely.
> 6) Suppose that I have a wordlist of almost 70GB. In this case the memory
> of motherboard and memory of graphical card will influence a lot or not?
Host memory is cheap so you should have a lot, I'd say at least 16GB.
GPU memory is not that important right now. As long as you have a couple
GB you're fine, 16 GB is not needed for anything right now but it *may*
be beneficial at some point in the future.
> 7) Does it worth to use two GPU cards together? Should they be connected
> via crossfire? Or not? Is there any specific advantage for password
> cracking with jTr?
Crossfire/SLI are for producing video. JtR can use multiple devices
regardless. If your OpenCL driver serves us one or several cards, we can
use them.
> 8) Finally, I'm very concerned about power supply and cooler. What do you
> guys recommend for a safe setup to keep this box running for week without
> temperature issues? :)
The GPU should blow its heat *outside* the case like the reference
designs do. For some reason many of the hip OEM models with lots of
bells and whistles doesn't. These are badly designed toys IMHO.
> a) Should I consider a watercooler for my processor?
I think not. As Gosney put it, "when it fails, it fails spectacularly"...
magnum
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