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Date: Mon, 20 Sep 2010 12:47:24 -0400
From: Charles Weir <cweir@...edu>
To: john-users@...ts.openwall.com
Subject: Re: Substitution ciphers

Hey Rich,
    I really doubt that JtR could be configured to deal with this
since you require a human to determine if the code was cracked or not.
Aka you need to look at the plain-text and say, "ah that looks right".
That's different from a password hash which JtR can check
automatically, (hashing a guess and comparing it to the target hash).

I highly recommend that you check out CrypTool. I've used it in a
bunch of computer security challenges and had great success with it.
You can visit the website at:

http://www.cryptool.com/

I still use the older version of it just because it's simpler for
dealing with basic ciphers, (and I'm lazy), but if you are willing to
learn some of the advanced features the newer version is pretty nice.
They even have a web-only version though it's a bit limited. Just
curious, do you know if you are dealing with a substitution cipher or
a vigenere cipher? They are actually a bit different in that a
vigenere cipher can encrypt the same letter differently depending on
the key length, (technically a vigenere cipher with a key length of
one is the same as a substitution cipher). Therefore, it's usually a
pain to break smaller messages encrypted with it, (you need enough
ciphertext to be able to perform frequency analysis on each
substitution cipher in the vigenere cipher's key).

Matt

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