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Date: Wed, 18 May 2011 12:14:09 -0600
From: RB <aoz.syn@...il.com>
To: john-users@...ts.openwall.com
Subject: Re: Help with 14 - 16 digit CC's stored in MD5 hash
On Wed, May 18, 2011 at 10:45, Kevin Finisterre <kf@...italmunition.com> wrote:
> Can anyone direct me to optimal configuration settings for JtR when attempting to reverse credit card information that is stored in MD5 hashes? The numbers are assumed to be 14-16 digits in length.
An interesting problem, but one fraught with danger for both requester
and helper.
> Theory associated with what I would like to accomplish is can be found here.
> http://www.integrigy.com/security-resources/whitepapers/Integrigy_Hashing_Credit_Card_Numbers_Unsafe_Practices.pdf
>
> The paper mentions several techniques as well as rainbow tables. I am looking for anyone that has actually generated tables specifically geared toward this attack or for anyone that can offer configuration tips for JtR. Helping John make more efficient guesses would be the key, implementing logic from the paper would be quite useful.
Didn't read the paper because I'm lazy and paranoid (a fantastic
combination, I might add), but optimally you'd need to do several
things:
- allow for larger candidates than the default 8
- filter candidates based on known issuer formats & mod10
- produce numeric candidates only (obviously)
Sounds like a job for an external filter initially, I doubt there'd be
enough regularity in such data as to make a new full-fledged format
necessary.
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