🚀 go-pugleaf

Hi,

I'm currently working on a project which involves the design of a DES cryto-
chip. When reading some papers on this subject, it appeared to me that there
is a great need for enlarging the number of bits used in the cipher key. I read
about an implementation of the DES with a cipher key of 768 bits in the paper
of T.Kropf, J.Fr"ossl, W.Beller and T.Giesler: A hardware implementation of a
modified DES-algorithm, in North-Holland Micorprocessing and Microprogramming
30, 1990.

Questions:

  1)  Does anybody know the reason(s) for the number of circular left shifts
      which are performed on the cipher key each iteration in the original
      DES algorithm ?
  2)  Does anybody know of other modifications concerning the key size ?
  3)  Do modifications exist which have been published or proposed by the
      NBS, or do other (de facto) standard modifications exist ?

I surely hope someone is able to answer my questions. Thanks in advance,


Bartjan Wattel at Eindhoven University of Technology, the Netherlands
(Email: bartjan@blade.stack.urc.tue.nl)
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