outer@utcsrgv.UUCP (Richard Outerbridge) (02/27/84)
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