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Date: Tue, 20 Nov 2012 07:00:17 +0100
From: Frank Dittrich <frank_dittrich@...mail.com>
To: john-users@...ts.openwall.com
Subject: Re: How does incremental mode works?

On 11/19/2012 04:39 PM, Richard Miles wrote:
> Sorry, I was not clear on my previous e-mail. You are correct, it's
> possible to specify the pass at john.conf - however, I would like to pass
> this parameter via command-line.
> 
> At documentation and even at config file is described that no command-line
> is available, but I'm just curious why not? I mean, I don't believe there
> is a technical limitation. Is there a chance to add it to the TODO list?
> Magnum does a great job and constantly improve jTr command-line options,
> can you consider it please? :)

Actually, I don't think this is a good idea.
Given how hard it is to produce a good stats file, you shouldn't use an
endless number of different stats files anyway.

Incremental mode is similar.
You can't specify the .chr file, minimum and maximum length, number of
different characters on the command line.
Instead, you can just specify which incremental mode to use (using
--incremental=MODE, if the default isn't what you want), and the details
are defined in a config file section.

When Simon initially implemented Markov mode, there was no way to use
different stats files for several john sessions running in parallel,
unless you used separate directories.
When --config= has been added, you could at least use different stats
files when using different config files for your john sessions.

So when I changed Markov mode, I intended to enhance the functionality
(easier way to use different stats file, optionally specifying a
percentage  instead of absolute numbers for START and END) and to make
using it more similar to using incremental mode, so that you could just
use --markov=MODE.
I kept the "legacy" way to specify different Markov mode parameters
directly on the command line just to maintain backwards compatibility
for users who want to restore Markov mode sessions that have been
started in older john versions, or for advanced users who use genmkvpwd
in a script which calculates the Markov mode level and the START and END
values to create john sessions.
Because it wasn't that difficult to implement, I even supported
combining the name of a Markov mode and specific Markov mode parameters
on the command line. Since all the Markov command line parameters were
optional, I couldn't allow Markov mode names which were also valid
Markov levels.
Trying to allow a stats file being specified on the command line would
have made matters even more complicated.

Frank

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