On Thu, 28 Oct 2004 01:00:56 +1000, "David Eather" <eat...@tpg.com.au>
wrote:

I'm the one who invented NEWDES "decades" ago.  I must admit that I
did not know much about cryptography back then, beyond what I learned
in a Helman seminar.  The algorithm was intended to address what was a
concern at the time for DES - the transparency of the design.  People
were concerned about the possibility of trap-doors known only to the
designers.  For that reason I chose to develop a random S-box based on
the text of the Declaration of Independence, as described in the
original Cryptologia article.  A carefully crafted S-box may have
produced a stronger algorithm, but it would not have passed the test
of transparent design.

I must admit that NEWDES is not very good, especially in light of all
the better choices now available.  I thought that having complete
diffusion of a single bit change in seven rounds was good enough, but
when there are only 17 rounds, that just isn't enough diffusion.  If I
were to modify it now, I would either add more rounds, or change the
round function so that complete diffusion happens in just three or
four rounds.  Another thing I would change would be the key expansion
schedule.  It is too simple - even with the 1996 modification.
Finally, I would change some of the exclusive-ORs to addition.  That
would introduce a little more complexity at no cost in computing time,
and at the same time it would avoid the complementation property that
NEWDES shares with DES.

-Robert Scott
 Ypsilanti, Michigan
(Reply through this forum, not by direct e-mail to me, as automatic reply address is fake.)