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Date: Mon, 14 Sep 2015 18:31:48 -0700
From: Fred Wang <>
Subject: Re: Judy array

On Sep 14, 2015, at 6:03 PM, Solar Designer <> wrote:

> Fred, magnum -
> On Sun, Sep 13, 2015 at 08:28:08PM -0700, Fred Wang wrote:
>> I use a 10-year-old Dell 2950 as my test environment, precisely because it uses slower memory, and more easily shows improvements.  For my "standard" test case (MD5, 29 million hashes, a ~13 million entry dictionary, and best64 rules, yielding about 1 billion hash attempts to find about 1.7 million solutions)
>> hashcat	3 minute 54 seconds
>> mdxfind	1 minute 15 seconds  (Judy only)
>> mdxfind	47 seconds  (Current code, Bloom filter + Judy)
> Fred - is this with the original best64 rules you e-mailed me, or with
> the cut-down version with only JtR-compatible rules left in it (14 rules
> removed)?  (BTW, this best64 is currently misnamed since it contains
> more than 64 rules either way.)

The cut-down version was used, and there are exactly 64 rules in it with your subtractions :-)

> magnum - testing this stuff, I see that pot sync is a major bottleneck.
> Since this is your feature, you might want to benchmark and optimize it
> some more, or/and maybe we just want it disabled by default when cracking
> saltless hashes.  As it is, it's just not able to handle Fred's "about
> 1.7 million solutions" in a minute - it takes several minutes to process
> those guesses, so it becomes the primary bottleneck for the whole run.

To test this, I took the 29m.txt file, and reversed each hash, so that no hashes would be found by John.  No finds, no output.

With best64, and --fork=32, I get a run time of 1:30.  For --fork=16, I get 1:28.

With mdxfind -t 32, I get 0:17.  For -t 16, I get 0:21

So, yes, the output hurts - but the rest of John is still many times slower than it needs to be.

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