From pmetzger at lehman.com  Mon Jul 12 20:06:58 1993
From: pmetzger at lehman.com (Perry E. Metzger)
Date: Mon, 12 Jul 93 20:06:58 PDT
Subject: xor data hiding?
In-Reply-To: <9307130230.AA20305@triton.unm.edu>
Message-ID: <9307130306.AA15377@snark.shearson.com>



J. Michael Diehl <mdiehl at triton.unm.edu> says:
>      I heard something interesting which made me think. (gasp)  
>  
>      I heard that if you encrypt a file with the xor encryption alg.
> multiple times with different keys, you get an encrypted file with a
> coorisponding effective key which has some interesting properties.  The key
> in such a system would have a length equal to the Least Common Multiple of
> the lengths of the original key.

Sadly, the Friedmans already cracked the "multiple repeating xored
keys" cypher a while back -- about fifty years ago.

Don't be embarassed, by the way -- everyone comes up with cyphers that
have been cracked before. However, I would suggest reading "The
Codebreakers" and the current literature before proposing new systems.

Perry