From: paul@fatmans.demon.co.uk
Date: Tue, 17 Sep 1996 11:25:09 +0800
To: cypherpunks@toad.com
Subject: Redundancy in XOR encryption
Message-ID: <842896374.27768.0@fatmans.demon.co.uk>
MIME-Version: 1.0
Content-Type: text/plain


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I have a question I hope someone here might be able to answer:

As the method of cryptanalysis of XOR (Ie. index of coincidence) 
relies on redundancy in the plaintext, would the following be strong:

Compress P to get perfect compression (ie. 0 redundancy)
Encrypt F (the compressed text) using a repeated key XOR

of course this is all rather theoretical as there is no such thing as 
perfect compression, but I just thought it might be interesting to 
see if this is indeed strong, superficially it appears so to me...


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  Datacomms Technologies web authoring and data security
     Paul Bradley, Paul@fatmans.demon.co.uk
       Http://www.fatmans.demon.co.uk/crypt/
         "Don`t forget to mount a scratch monkey"

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