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Date: Fri, 31 Jul 2009 22:42:37 +0400
From: Solar Designer <>
Subject: DumbForce external mode vs. incremental mode (was: invoking a DumbForce external mode)

On Fri, Jul 31, 2009 at 08:24:25PM +0200, websiteaccess wrote:
> Macintosh:run xxxxxx$ ./john -e=DumbForce-alpha-fr test.txt
> Loaded 1 password hash (FreeBSD MD5 [32/64 X2])
> guesses: 0  time: 0:00:00:02  c/s: 8611  trying: sdc - sdd
> guesses: 0  time: 0:00:00:03  c/s: 8618  trying: èué - èuè
> guesses: 0  time: 0:00:00:04  c/s: 8631  trying: ahjé - ahjè

This looks fine to me.

>  How JTR can crack a password "aselé" when trying only 4 letters ?????  
> :-/

It will get to trying 5-letter passwords when it is done with 4-letter
ones.  Ditto for even longer passwords.

You can't expect a DumbForce mode to be as smart about things such as
length switching as incremental mode is.  The reason why I suggested it
was that you did not seem to care about the order in which your
candidate passwords would be tried.  I indirectly inferred this from the
way you were placing your characters into a fake john.pot file for
generating a custom charset.  With that attitude, DumbForce appeared to
be a simpler way to achieve a similar effect.  You've since expressed a
related concern, but referring to not breaking pre-defined incremental
modes for other uses only.  You also did not mention that you'd be
attacking a relatively slow hash this time (you were dealing with raw
MD5 hashes before, which were roughly 1000 times faster).

If you do care about the order in which your candidate passwords are
tried, and now you appear to, then you need to go for a modified build
of JtR as we've discussed before, invest more time into preparing a more
optimal fake john.pot (tricky), then generate a custom .chr file and use
that.  You'd only use this build of JtR when you need your custom


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