john-users - Re: Password to guess with a lot of information

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Date: Thu, 6 Mar 2008 09:05:58 +0100
From: "L B" <bertignac@...il.com>
To: john-users@...ts.openwall.com
Subject: Re: Password to guess with a lot of information

Hello,


> 1. Define a 9-character alpha-numeric "incremental" mode (requires a JtR
> recompile and a custom .chr file).  Define an external filter() that
> will only let candidate passwords ending in two digits pass.  That is,
> when the "word" is unsuitable, set "word = 0".  Use both modes at once.


> 2. Define and use "incremental" for the first 7 characters (does not
> require a recompile, nor a custom .chr file).  Define and use an
> external filter() that will modify "word" by adding two digits to it.
> You'd have to do up to 100 invocations of JtR with different filter()
> functions - separately for each two-digit combination.
>


Ok, I understand. I managed to recompile john to guess a 9 characters
password, it's running. I see what you mean about external filters, it looks
smart, but I can't make them work (first experience on "external filters
programming")

I haven't tried your 1), but I tried 2) with a simple scenario of adding 00
at the end of my 7 characters long word, with filter_alnum as an example :

[Incremental:mypass]
File = $JOHN/alpha.chr
MinLen = 7
MaxLen = 7
CharCount = 26

# Some pre-defined word filters
[List.External:Filter_mypass]
void generate()
{
        word[7] = '0';
        word[8] = '0';
        word[9] = 0;
}
void filter()
{
        int i, c;

        i = 0;
        while (c = word[i++])
        if (c < 'a' || c > 'z') {
                word = 0; return;
        }
}

But it doesn't work. If you have any pointers, they are welcome !

-- 
L.B.