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Message-ID: <20120828224150.GA6761@openwall.com>
Date: Wed, 29 Aug 2012 02:41:50 +0400
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: JtR vs. hashcat on /r/crypto
On Tue, Aug 28, 2012 at 02:21:07PM -0500, jfoug wrote:
> >From: Solar Designer [mailto:solar@...nwall.com]
> >
> >2. It turns out (was news to me) that hashcat added SunMD5 support
> >recently (on CPU). According to atom, it does not use SIMD, yet is
> >faster than ours with SIMD (JimF's unreleased code in magnum-jumbo).
> >I've asked atom for specific speed numbers, but we might want to do our
> >own benchmarks as well (Jim?), if we don't mind running the closed-
> >source hashcat for that. ;-)
>
> I have a strong belief the coin flip logic we have (the original sun logic),
> is where the speedup can be found. Yes, we did remove a %5 in one of the
> loops. But there still has to be a LOT of optimization left. There is a lot
> of temp memory usage, and memory movement. It 'could' be some other factor,
> but I really think not. This is why I was surprised by only a 3.5x
> improvement when going to SSE2 code. I expected a much higher rate, since
> we modify that large buffer so little.
Well, it's 4.4x with XOP, but I wouldn't be surprised by a higher
speedup (over the original Sun code or equivalent) with further
optimizations on top of SIMD usage. What surprises me is that atom says
he achieved greater speed "by not using SIMD".
> Possibly there is something Atom was able to find, that busted the coinflip,
> and found some way to compute it in a deterministic (or nearly
> deterministic) manner.
Even if so, I don't see how that alone would provide more than a ~4x
speedup without going SIMD. Didn't the original Sun code use the
non-SIMD MD5 code fairly optimally (well, except for wasting a little
bit of time on the modulo division and such)?
Maybe I need to take a closer look at the code myself, but for now I'll
just wait to see the performance numbers for hashcat's SunMD5. Perhaps
someone can try it out and post in here?
Alexander
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