Last Call for Papers (extended): International Conference on Circuits
and Systems ICCS 2008
From: International Association of Engineers (IAENG)
San Francisco, USA, 22-24 October, 2008
http://www.iaeng.org/WCECS2008/ICCS2008.html

Important Dates:
Draft Paper Submission Deadline (extended): 22 July, 2008
Camera-Ready Papers Due & Registration Deadline: 30 July, 2008
WCECS 2008: 22-24 October, 2008

I am working through Schneier's self-study course, and am attempting 4-
round DES.

Here's where I am right now. I have managed to construct my DDTs for
all 8 S-boxes, and have followed a one-round characteristic with p=1
where if the XOR of the plaintext pair is 2000000000000000 then so is
the output XOR for that one round. I can see the 28-bits of 0 in the
output of the second round's F-function (all but bits 7, 16, 20, and
21) due to the 0'd inputs -- this gives me information about most of
the S-boxes for round 4.

I believe that the next and final step is to fix those bits that I
know in the subkey for round 4, and then try any remaining candidates
against my known plaintext pairs. (Since the characteristic has p=1,
any plaintext pair with that XOR should work as a "right pair") -- the
subkey that works with all of the pairs to produce the output will
give me all but 14 bits of the original key, and I can then use 2^14
trials to extract the whole key.