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Date: Fri, 10 Jul 2009 03:09:51 +0400
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: CHARSET_* compile-time settings & 64-bit non-overflow requirement (was: International Charactersets)

On Thu, Jul 09, 2009 at 03:01:34PM +0300, kalgecin@...il.com wrote:
> Could someone please explain more on this:
> /*
>  * Charset parameters.
>  * Be careful if you change these, ((SIZE ** LENGTH) * SCALE) should fit
>  * into 64 bits.  You can reduce the SCALE if required.
>  */

For others on the list - this is a comment in params.h, right above the
CHARSET_* compile-time settings.

> How do you check if it fits to 64 bits?

You could do the math, but luckily current versions of JtR will do the
correct safety check for you when you invoke the --make-charset=...
option.  So JtR will refuse to generate a .chr file if you set the
CHARSET_* settings in a way triggering the 64-bit overflow.  This safety
check is implemented in charset.c: charset_self_test().

In fact, the actual requirement, checked for in the code, is a bit less
strict than what the comment states (I didn't want to have the comment
overly-complicated).  So you may get away with slightly higher settings,
which is OK, as long as JtR doesn't complain.

Alexander

P.S. Please post your replies to the most relevant messages (not to
arbitrary messages in the thread, which was what you did), and please
don't over-quote.  I had to edit almost all of your postings in the
moderation queue, removing extra quoting.  If you find yourself quoting
the mailing list manager's automated unsubscribe notice (which you did
all the time you were replying!), then you're definitely doing something
wrong - and I won't let such a posting through without having to edit
the quoting first (which I'd rather not be spending my time on).  I hear
that Gmail makes it too easy to over-quote by hiding quoted text, yet I
ask you - and all others - to be careful to quote relevant context only.

http://www.netmeister.org/news/learn2quote.html

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