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From: ritter@io.com (Terry Ritter)
Newsgroups: sci.crypt

Subject: Re: Doing Better than XOR in RC4-like Algorithms
Date: 18 Nov 1994 14:35:53 -0600
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 In  padgett@goat.orl.mmc.com
 (Padgett 0sirius) writes:

>Near as I can tell (not sure the citation was in english) that covers any
>forward substitution scheme in which the final transformation is a function
>of a cyclical algoritm which include the previous block as a component. That
>would seem to include (among many other things) DES, the Enigma, and a
>forward transformation use of the Little Orphan Annie Secret Decoder Ring.
>
>Am I missing something here ? (Ignorance is curable).

 Well, first of all, we might try to parse the above:

      forward substitution scheme in which the final transformation
      is a function of a cyclical algoritm which include the
      previous block as a component.

 What *is* a "forward substitution scheme"?  Are there *backward*
 substitutions?  How do backward substitutions differ from forward
 substitutions?  Is a substitution a transformation, or vise vera?
 Is DES a "substitution scheme?"  Is exclusive-OR a "substitution
 scheme?"  What *is* a cyclical algorithm?  And so on.

 My point here is that it is a non-trivial exercise to try and
 define technical mechanisms precisely.  Patentese may fail to
 do so, but compare it to ordinary writing and one can see certain
 advantages.

 If the problem here is the outrageous possibility of a patent
 itself, be aware that virtually all significant technical advances
 (including cryptographic advances) *are* patented.  This is the way
 the organizations which employ cryptographers (or other designers)
 protect and profit from the work.  It is also one way in which I
 personally attempt to profit from the years of my life, the sweat
 of my brow, and the investment from my own pockets.  I am not going
 to be real happy to be told this is immoral.

 The Dynamic Substitution patent covers cryptosystems which have a
 table of substitute elements, encipher a character through that
 table, and then re-arrange elements within the table, after every
 enciphering.  It seems unlikely that any mechanical scheme could
 do this.

 ---
 Terry Ritter   ritter@io.com