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Message-ID: <20131121051912.GA31175@openwall.com>
Date: Thu, 21 Nov 2013 09:19:12 +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 Tue, Nov 19, 2013 at 11:47:47PM -0600, Richard Miles wrote:
> a) They clearly state that Radeon cards are much faster. My question is,
> this information is still true recently?
Yes, with few exceptions (NVIDIA is also OK at hashes based on SHA-512).
> b) I have heard that Radeons drivers sucks and are very unstable. Is that
> true?
Yes, but certain lucky driver versions mostly work fine. e.g. Catalyst
13.11beta1 seems mostly fine (although we might not have tested it
enough), 13.11beta6 is not. For an older GPU (not requiring very recent
Catalyst versions), 13.4 should be mostly fine.
> c) What is JtR actual support for Radeon cards? At the moment and further
> efforts are better Radeon or Nvidia?
You just choose the GPU that is faster for your hash types. At mscash2
that you mentioned, AMD GPUs are a lot faster than NVIDIA.
> 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?
I recommend 7970. New reference 7970 GE can still be bought, despite
what magnum said. ;-) They're also inexpensive now. You might buy two
for the price of one R9 290X.
R9 290X is faster than one 7970, but is more of an experimental option
now (fewer suitable Catalyst versions, etc.) You may try it, though.
We will.
7990 has cooling problems itself (have to underclock its GPU0, except in
server chassis with fans forced to "Full"), and will additionally heat
up the rest of your components (again, unless in suitable server
chassis). Water-cooling solves this, but costs a lot (could buy more
GPUs instead) and is risky. 7990 requires at least Catalyst 13.6beta
(won't run with 13.4).
6990 is outdated. Not much faster than 7970 (if at all; depends on hash
type), but costs more, produces more heat, and has little overclocking
potential (7970 has a lot).
> e) Is is possible to do overclock on processors and GPU cards under Linux?
Yes.
> Is it recommended?
Not really. There's usually more to be achieved by focusing your
attacks than by increasing the speed of your machine, not to mention the
risks, extra heat, and extra noise. There are some rare exceptions to
this - e.g., if you were to crack bcrypt hashes on 7970s for some reason
(just don't have a lot of CPUs and happen to have these GPUs
idling), overclocking them is OK (and for this hash type does not result
in any heat and noise - the GPU stays cool and silent, since only 1/4th
of it can be used for bcrypt cracking anyway).
> What tools are available?
For CPU, you control the overclocking (mostly) via BIOS setup settings
(so not in Linux, but they remain in effect for Linux). Some
motherboards also let you overclock on the fly with buttons on the
motherboard itself. For AMD GPUs, you overclock (or underclock if
necessary!) with amdconfig (command-line tool included in the Catalyst
driver package).
> f) Finally, based on your suggestion of GPU card, what are the current
> password hash formats supported?
The "slow" ones from the list that magnum posted - the various Unix
crypt(3) hash types, mscash2, some encrypted archives, etc.
> 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?
Yes, with all modes - but the candidate passwords are generated on the
host CPU, so this is efficient for inherently slow hash types only.
> 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?
No, unless you install more than 70 GB RAM, although when cracking fast
hashes it makes sense to keep that wordlist on SSD (if you have one).
> 7) Does it worth to use two GPU cards together?
You may, e.g. to run two attacks at once efficiently. You tell one
instance of JtR to use --device=0 and the other --device=1. In
bleeding-jumbo, you may also have one attack use both GPUs with
"--fork=2 --device=0,1" (requires recent Catalyst).
> Should they be connected via crossfire?
No.
> Is there any specific advantage for password cracking with jTr?
Of multiple GPUs? No. One faster GPU is better than two slower ones,
but if you want total performance better than that of one fastest GPU,
you have to use two or more.
However, 2x7970 is better than one 7990 in terms of cooling. 7970's
blow hot air to outside of the case, 7990 inside. Dual-GPU cards like
6990 and 7990 look to software as two GPUs anyway, though (so you have
to use the --device option as if you had two cards).
> 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? :)
GPU cards that blow hot air to outside of the case (7970 is great).
CPU with sane TDP (perhaps up to 95W). Decent air cooling.
> a) Should I consider a watercooler for my processor?
I would not, unless you choose a CPU with excessive TDP or/and overclock
it a lot. The only reason to water-cool a normal CPU would be to reduce
the noise, but would you also install a water block on your GPU? If
not, your system would not be silent anyway (not when GPU is in use at
least). And if you do, it'd cost and increase the risks.
> b) Should I consider a special cooler for GPU card?
I recommend that you choose a GPU card that works well with stock
cooling. 7970 is great, 7990 is problematic.
> I was thinking about the following potential configurations:
>
> Processor: Core i7 (4770) - 3.40GHz Quad Box (intel)
That's good, but if you consider overclocking at all then go for 4770K
instead. 4770K is 100 MHz faster (and so is 4771) and has unlocked
multiplier (can easily be overclocked to 4+ GHz on air). These are
84W TDP. Another option that I guess you could afford is 4930K (on a
suitable motherboard), which is 6-core (12 logical), but it's 130W TDP
and only 66.8C max temperature, so may be a pain to cool.
> Motherboard: GA-H81M-S2PV (Gigabyte)
This only works for a single GPU. I suggest that you pick a motherboard
that will let you upgrade to multiple GPUs (perhaps to 4), so you need
multiple spaced out PCIe x16 slots. You may also need a big tower case,
so that the bottom slot is not too close to the bottom of the case
(otherwise a dual-slot card won't fit in this slot and you'd waste it).
> GPU: Radeon HD 7970 3GB GDDR5 384-bit (AMD) (2 units)
OK, but you really need a different motherboard for "2 units".
> Power Supply: 800W | GS800 V2 (Corsair)
800W PSU is OK for that system with two GPUs (650W is minimum for it),
but for upgrading to 3 or more you need more power.
> Processor: AM3+ TDP 125W - Piledriver FX8350 4.0GHz Octa-Core (AMD)
AMD FX CPUs' computing power is not worth the 125W (Intel's do more per
Watt), and it can be a pain to cool. I gave up long ago on trying to
keep FX-8120 under its stated 61C maximum, going for ~70C instead (works
fine, though). You could with water-cooling, but that has its own
drawbacks.
If you were to purchase one of these anyway, a curious/crazy option
could be to get FX-9590, but underclock it to FX-8350 clocks (to stay in
under 125W TDP). The rationale is that FX-9590 are the better bins, so
they _might_ actually run cooler (yet accept higher temperatures without
damage to them) at 8350's clocks than actual 8350's do. From a costs
point of view, this makes sense since 9590's are currently available for
only a little more than 8350. No, I am not seriously suggesting this to
you - more like to someone else who would like to experiment and post or
blog about the results for everyone's amusement. ;-)
Overall, 4770K will deliver same or better speeds (most of the time) at
much lower TDP, and 4930K will be much faster at similar TDP (but it
costs more).
> Motherboard: GA-970A-DS3P (Gigabyte)
> GPU: Radeon HD 7870 2GB GDDR5 256-bit (AMD) (3 units)
That motherboard won't accept 3 GPUs.
If you want to save by purchasing GPUs smaller than 7970 (and don't mind
using up some motherboard slots that way), consider 7950 (compare prices).
7870 GE is too small. (7870 XT + overclocking could be OK, but you're
unlikely to buy it and overclocking is not nice.)
Alexander
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