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Date: Fri, 13 Jul 2012 22:51:46 +0200
From: Frank Dittrich <>
Subject: More features for MJohn


I think we still need something to keep all
clients busy doing something useful, may be a way to configure a client
to automatically fetch new attack descriptions and run them.

Letting the clients instead of the server initiate the connection will
help in a contest environment, where many users may be behind a NAT router.

This minimal functionality is a first step. An enhanced version should
take into account number of CPUs/GPUs, amount of main memory, free disk
space, to descide which kind of formats to attack, how many attacks to
run in parallel, and so on.

E.g., for a CPU with 4 cores and hyperthreading, useful options would be:
-just 1 session at a time with OMP_NUM_THREADS=4, for highly optimized
formats that scale well.
-just 1 session at a time with (default for such a machine)
OMP_NUM_THREADS=8, for formats that support OMP, but are not optimized
-4 different sessions for formats that are optimized, but don't scale
well with OMP or lack OMP support (in this case, a john build without
OMP support should be used).
-just 1 session, but split across 4 cores (requires --fork= / --nodes=
to be supported)

There is no need to implement everything at once.
Start with just fetching a task from the server that has not been
started, mark it as started on the server.

To define priorities for the tasks (which tasks to run/transfer to a
(/which) client in what sequence), we either need some voting system, or
we need to set priority based on success of previous attacks defined by
the same user.
Measuring/comparing the success might be tricky, because usually success
changes over time.
When you start, it is easy to crack passwords, then it gets harder until
you identify a new pattern, and so on.

The voting can also be mimicked by an assessment at the begin of the
pen test / contest (which formats will be the easiest to attack first /
which formats will likely give most points).


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