🚀 go-pugleaf

In article <4051@megaron.arizona.edu>, mike@arizona.edu (Mike Coffin) writes:
> From article <996@sdcc13.ucsd.EDU>, by ln63wgq@sdcc13.ucsd.EDU (Keith Messer):
> > I don't expect I'm even close to the smartest person who's worked on the
> > problem, but if my approach isn't going to work, I'd like to hear why.
> > Perhaps you have a really nifty job and are a bright guy, but you're acting
> > like a geek.
> 
> I guess this is directed at me, despite the subject line.  Well, I
> don't have a nifty job --- I'm just another lowly grad student --- but
> I don't see how I was acting like a geek.  I didn't even say your
> approach wouldn't work.

Ingrid Schaumuller-Bichl of Austria had a paper in Eurocrypt 82
(actually Lectures Notes in Computer Science #149, Cryptography, by
Springer-Verlag, 1983) about finding the complexity of DES (DEA in
Europe) by representing each output bit as an XOR-sum-of-products (an
idea originally due to M.E. Hellman of Stanford in 1976).

He was able to make significant progress on S-P systems using linear
S-boxes, and also gives the XOR-sop exprfessions for each of the 8
S-boxes.

His conclusion was that the computers fast enough and large enough to
simplify the polynomials that arise would probably be able to
"brute-force" search the DES key.  He also suggested a meet-in-the-
middle attack where the intermediate variables after the 8th round of
substitution/permutation are expressed in terms of both the inputs and
the outputs, giving a far simpler system of 64 equations in 56 unknowns.

So Keith, keep plugging on that simplifier, because that's a good idea.
And Mike, lighten up.  If he doesn't know how hard a problem he's
working on, he might just solve it.

And let's not call each other geeks, okay?

Michael L. Mauldin (Fuzzy)		Department of Computer Science
ARPA: Michael.Mauldin@NL.CS.CMU.EDU	Carnegie Mellon University
Phone: (412) 268-3065			Pittsburgh, PA  15213-3890