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Date: Fri, 18 May 2012 13:31:35 -0500
From: "jfoug" <>
To: <>
Subject: RE: Performance Considerations of stdin

>From: Brad Tilley []
>What, if any, performance considerations are there when passing word
>candidates to JTR via stdin? I plan on doing some tests to see first-
>hand, but before doing so I wanted to ask here in case others have had
>some experience with this.
>Basically, I'm wondering if a word generation program that passed words
>into JTR via stdin would perform better than when JTR is doing both word
>mangling and hash generation, hash testing, etc all by itself.
>ehco -n word | john --sdtin
>Has anyone had experience performance testing something such as this?

Depends upon the OS.  If it is winblows, then the performance is horrible.
I get about 30% or so performance for fast hashes, vs a dictionary read into
memory, with rules run on the dictionary.  Windows has a TINY pipe_buffer.
I have found no way to speed this up (and I have tried).

However, for many other OS's, may likely be a performance boost by using
-stdin mode, IF doing some complex work, since you can do much more complex
things a lot more efficiently in a native language (like C, or even perl),
much faster than john's rules.  

I have done this for things like a super elite builder, which can do all
sorts of permutations, such as full permutation of letter case, case, full
permutation of all elite possibilities (such as mississippi -> m1ssissippi,
miss1ssippi, m1ss1ssippi, ... m!ssiss1pp|, etc).  Doing this in john, with
rules, or other extern stuff 'could' be done, but that is beyond my
capabilities, and I think you would either have to write a lot of rules that
either reject a lot of input words, looking for specific patterns, or the
rules would generate a lot of dupes.

I also did this, for a much more heavily complex time/date generator, that
did an all in one type run, and could handle much more than the external
date_time code in john.conf.

I would love to hear any speed comparisons between 

john -rules:xxx -memory=9999999 -w=input.dat
word_gen input.dat | john --stdin

where the --rules:xxx (or externs, etc) and word_gen were 'comparable', when
run on other OS's.


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