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Date: Sun, 21 Aug 2011 15:41:37 +0200
From: "madfran" <madfran@...-ezine.org>
To: john-users@...ts.openwall.com
Subject: Re: Some problems to build chr
Hi,
> Well, this is definitely becoming a FAQ. :-( We can't bring the same
> topic up every 3 days, can we?.. It's like the third time this week.
Perhaps the explanation is not very clear,... or perhaps the students
are not so intelligent :-)
> > # ./john --make-charset=lanman.chr
> > Self test failed (pow64of32() overflow)
>
> This means that you set the params.h settings too high, beyond what's
> supported. Please read the lengthy comment right before your edits.
> Also, see this older posting for sample valid settings:
>
> http://www.openwall.com/lists/john-users/2007/07/04/6
>
In my poor opinion, the referenced posting not give a so clear
explanation. Perhaps better information is in the comments of
params.h
* Please note that certain intermediate values computed in charset.c
while
* generating a new charset file should fit in 64 bits. As long as
* ((SIZE ** LENGTH) * SCALE) fits in 64 bits you're definitely safe,
although
* the exact requirement, which you can see in charset.c:
charset_self_test(),
* is a bit less strict. John will refuse to generate a charset file
if the
* values would overflow, so rather than do the math yourself you can
simply
* let John test the values for you. You can reduce the SCALE if
required.
If I understood well, to avoid a overflow:
((SIZE ** LENGTH) * SCALE) must fit in 64 bits.
That means ((SIZE ** LENGTH) * SCALE) < 2**64
So, if I want to cover the complete range of characters (FF) the max.
size must be 8 and the scale 1.
256**8*1 = 2**64
I am right?
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