Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Wed, 1 Feb 2006 16:22:34 +0300
From: Solar Designer <>
Subject: Re: Incremental Alpha Quagmire

On Wed, Feb 01, 2006 at 04:27:59AM -0800, Arias Hung wrote:
> Then what would be the proper way to create an 'optimized' UpperLower.chr
> or is that beyond the scope of explaining here?

The proper way to generate .chr files is to use samples of real
passwords.  If you're able to get some passwords from your target system
cracked, then you should use that john.pot to generate your .chr file -
and do not restrict it to just letters.

If you're not able to get any passwords cracked, then you don't know
what characters are actually common in those passwords.  Your saying
that uppercase characters are very common is pure speculation.  This may
or may not be the case.  If you'd like to make this assumption anyway,
you can convert some cracked passwords from another system (or just
words from a wordlist) to upper or mixed case and place those in a fake
john.pot (preceding each entry with a colon), then generate a .chr file
out of that.  But it would be a hack that is only marginally better than
what I had explained previously.  (It is better because it does not
consider different letters to be equally probable - it only does that
for upper vs. lower case.)

> Would you consider adding this as an option

Well, I could generate a .chr file with the 52 characters, but it would
consider lowercase letters to be far more common than uppercase ones
(because they _are_ far more common).

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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