🚀 go-pugleaf

phr@telebit.com (Paul Rubin) writes:


>1. It's not known (that I've heard) that multiple DES is half the
>set of all encryptions.  What's known is:
>  1) (single) DES is not a group.
>  2) The *single round* DES functions generate half of the set of
>     all encryptions (i.e. permutations of the 2^64 text blocks).

Uh, there are 2^56 single round encryptions and (2^64)! permutatons. The
first is "slightly" smaller than the second.

>2. I don't see a simple argument that even if DES generates A_(2^64)
>(i.e. half of all the permutations), double DES contains anything
>like 2^112 of those elements.  It's a reasonable thing to guess, but
>I'd like to hear some actual evidence...
 Yes it was a pure guess. It would be interesting to see evidence. As I
 said, DES would have to be almost a group ( D1 D2=D3 for many D in
 DES) for my estimate to be false.