john-users - MPI with incremental mode working fine?

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Date: Mon, 10 Sep 2012 22:21:38 +0200
From: "Thireus (Thireus.com)" <contact@...reus.com>
To: john-users@...ts.openwall.com
Subject: MPI with incremental mode working fine?

Hi everyone,

I was wondering if the current MPI implementation is working fine with incremental mode.
I have just created a new custom incremental mode based on a custom generated charset.

[Incremental:custom]
File = $JOHN/custom.chr
MinLen = 8
MaxLen = 16
CharCount = 94

And I notice from the john output that I have duplicated passwords. As far as I can tell some passwords (not all) are repeated/calculated twice.
Because I'm using saved sessions, I would like to know if there's a way to check that the password space is well divided in 8 parts. How can I manage to check this from the session.X.rec files ?

I currently have some clues about this issues... but there are just suppositions:

1- MPI not working at all for incremental mode, and because passwords are saved into john.pot every 10 minutes, the current 4 cores are desynchronized leaving only 1 core (2 threads) to be the leader, so that's why passwords are found twice.
2- The algorithm does not split very well the password space.
3- My saved sessions are corrupted.

I have this issue under john-1.7.9-jumbo-6 and john-1.7.9-jumbo-5, I have not tested other releases.

Also does the MPI implementation depend of the used hash format? (I had to create a custom dynamic hash algorithm)

Thanks for your replies :)

Regards,
Thireus (contact@...reus.com), 
IT Security and Telecommunication Engineering Student at ENSEIRB-MATMECA & Master 2 CSI University of Bordeaux 1 (Bordeaux, France).
http://blog.thireus.com