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Date: Wed, 12 Jun 2013 19:30:34 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: Mask mode for GPU

On 12 Jun, 2013, at 17:49 , Sayantan Datta <std2048@...il.com> wrote:
> I read about the mask mode from here:
> http://hashcat.net/wiki/doku.php?id=mask_attack
> 
> The mask mode explained above is I guess slightly different from what we need for GPU. Alexander mentioned before we need to take into account the keys generated on cpu. Then use the mask to multiply the keys in GPU.  
> 
> To implement mask mode what are the parameters that we need to take from user? e.g keyspace size, mask etc ?
> 
> How do we apply the mask on the keyspace ? For example: when I get a key say 'abcdefgh'(generated on cpu)  and a mask say '?d?d' at what position in the key are we supposed to apply the mask ? Do we append the mask or replace the charters at those positions ?
> 
> Please discuss these issues.

I had hybrid attack (http://hashcat.net/wiki/doku.php?id=hybrid_attack) in mind but I think we can enhance it: A really flexible solution would be using eg. the ?w mask for representing the original word (from another mode, eg. wordlist). So using HashCat's example, this wordlist:

password
hello

and this command-line:

./john -wordlist:file -mask=?w?d?d?d?d

...would generate the password0000..hello9999 candidates. We could also use eg. -mask=?d?d?w?d?d which is not supported by HashCat's hybrid mode.

magnum

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