Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site utcsrgv.UUCP
Path: utzoo!utcsrgv!outer
From: outer@utcsrgv.UUCP (Richard Outerbridge)
Newsgroups: net.crypt
Subject: DES as Simple Substitution?
Message-ID: <3368@utcsrgv.UUCP>
Date: Mon, 27-Feb-84 01:08:48 EST
Article-I.D.: utcsrgv.3368
Posted: Mon Feb 27 01:08:48 1984
Date-Received: Mon, 27-Feb-84 01:29:49 EST
Organization: CSRG, University of Toronto
Lines: 14

The DES, which operates on 64-bit blocks with a 56-bit key, can be viewed as
selecting between 2**56 simple substitutions on an alphabet of size 2**64 (at
least when operating in Electronic Code Book Mode).  This is presumeably NOT
unrelated to the fact that the per-character entropy of English (at least) does
not decrease much beyond octograms.

Considering that there are (2**64)! possible simple substitutions on the 
alphabet of 2**64 "characters", is it possible that a relationship exists
between the 2**56 substitutions selectable by the DES, analagous to the
relationship that exists between the 26 simple substitutions selected by the 
Vigenere tableau?  I've never seen this aspect of the DES examined (though I
have no idea how one would look for it...).

Richard Outerbridge 	outer@utcsrgv	UofToronto CSRG