🚀 go-pugleaf

mrosing@igc.org (Mike Rosing) writes:
: 
: Howdy,
: 	I'm totally new to this topic so please bear with me.  I've
: read several Springer-Verlag "lecture notes in computer science"
: including "Modern Cryptology A Tutorial" and a few of the Crypto' and
: Eurocrypt articles.  Crypto '89 has an article called "Good S-Boxes
: are Easy to Find" by C. Adams and S. Tavares.  I'd like to improve the
: DES routine I've got working already by substituting the s-boxes with
: some of the ideas described in this article.
: 
: 	The article states that there are 60 s-boxes which meet
: the criteria of 1) bijection, 2) nonlinearity, 3) strict avalanche,
: and 4) independance of output bits.  Only 3 of these are listed in
: the article and I don't have access to the J. of Cryptology to
: see if the authors actually got to publish a more detailed description.
: Does anyone have a listing of these 60 "perfect" s-boxes?

It is now known that the S boxes in standard DES are about the best
that can be done.  Biham and Shamir's article "Differential
Cryptanalysis of the full DES" explains this in more detail.  As far
as I can remember, the "perfect" S boxes have other weaknesses.

: 	Also, the article states "A simple way to extend DES in
: the short term might be to standardize a list of good s-boxes and have
: as part of the key the choice of s-boxes to use."  Has anyone done
: this and would you mind telling me how you used the key to pick
: the s-boxes?

This is a bad idea; see the above article.  In general, DES is very
well designed.  Any minor perturbation, even reordering the S-boxes
without changing them in any way, greatly weakens DES.  It's worth
looking at more recent CRYPTO and EUROCRYPT proceedings, as there is
much more on this subject.

: 	Finally, does anyone know how to get email to the above
: authors?  They are listed as being from Queen's University in
: Kingston Ontario.  Thanks for any replies!
: 
: Patience, persistence, truth,         reality:       mgr@anhep2.hep.anl.gov
: Dr. mike                                 UUCP:    uunet!pyramid!cdp!mrosing
: IMI, P.O. BOX 2242, Darien IL 60559    bitnet:              mrosing@igc.org

Andrew.