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Date: Wed, 23 Aug 2006 08:35:52 +0400
From: Solar Designer <>
Subject: Re:  "Extra" in incremental mode not fully working

On Tue, Aug 22, 2006 at 06:05:09PM +0000, Radim wrote:
> I've recently tested something like this:
> File = $JOHN/alpha.chr
> MinLen = 0
> MaxLen = 5
> Extra = ...

Your message has arrived with charset=utf-8.  Although you've mentioned
that you've been using "codepage win1250", I am not sure what 8-bit
character values you actually had in your john.conf.

> and then only some of the national characters were processed properly

What version of John?

Anyway, this should have worked as long as the total number of different
characters (those coming from the .chr file and those you've added with
Extra) doesn't exceed CHARSET_SIZE (95 by default).

> It brings me to another question: Is there an easy way to hack the params.h to 
> enable national characters in charset files?

You can try these settings:

#define CHARSET_MIN			' '
#define CHARSET_MAX			0xFF
#define CHARSET_LENGTH			8
#define CHARSET_SCALE			0x10

that is, you change CHARSET_MAX from 0x7E to 0xFF and CHARSET_SCALE from
0x100 to 0x10, leaving the rest at the defaults.  Of course, you'll be
forced to generate new .chr files.

Some john-users might notice that with the above settings we're
actually slightly exceeding 64 bits for ((SIZE ** LENGTH) * SCALE),
which the comment say to not do.  However, in reality the requirement is
not so strict; I just picked a simpler description for the comment.  The
self-test performed by current versions of JtR makes sure that things
don't go wrong - if there are overflows, JtR will refuse to generate
charset files rather than generate them incorrectly.

Alexander Peslyak <solar at>
GPG key ID: B35D3598  fp: 6429 0D7E F130 C13E C929  6447 73C3 A290 B35D 3598 - bringing security into open computing environments

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