🚀 go-pugleaf

One possibilty is to use a foriegn publisher. As an 
example, both FORTRAN and Pascal DES algorithms are published
in:

_Numerical Recipes: The Art of Scientific Computing_
Press, Flannery, Teukolsky and Vetterling.
Cambridge University Press.

A book that is highly recomded in spite of the poor 
implemetation of DES ( 1 bit per integer ).

Actually, I cannot see how a conviction could be obtained
given the wide distribution of the DES algorirthm even it
it were illegal. I would also be very surprised ( well
perhaps a little bit surprised ) if any government agency
would dare to set a precedent with DES given the great
risk of losing the case. Not to mention becoming known
as real idiots.

Don Martin  martin@entropy.ms.washington.ms

In article <770@entropy.ms.washington.edu> martin@entropy.ms.washington.edu (Don Martin) writes:
>A book that is highly recomded in spite of the poor 
>implemetation of DES ( 1 bit per integer ).

Why do you consider that a poor implementation decision?
It's the way I would have done it.  Packed bits would be
too slow.

Poor was a ill chosen phrase. The Numerical Recipes DES is
quite slow but portable by using one bit per iteger. If
bit packing were used, then it should be faster. Also, it
would be pretty easy to use a variant of the integer algorithm
to do 16 or 32 blocks in parallel.

In article <7343@brl-smoke.ARPA> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
>In article <770@entropy.ms.washington.edu> martin@entropy.ms.washington.edu (Don Martin) writes:
>>A book that is highly recomded in spite of the poor 
>>implemetation of DES ( 1 bit per integer ).
>
>Why do you consider that a poor implementation decision?
>It's the way I would have done it.  Packed bits would be
>too slow.

It's more fun to keep them in 48-bit words (or 32 if that's all you've
got) so that you can do operations on them a word at a time.  For the
permutations, for example, you can precompute the result of the permutation
applied to each byte in each position, and OR them together.  The XOR
operations happen immediately, of course.  Hauling 6- or 12-bit chunks
out to stuff through S-boxes (or doubled S-boxes if you have the luxury
of lots of memory) is simplified if you're using the 48-bit size, but
can be handled with a few shifts and logical operations without much
trouble even with 32-bit words.

Somebody (Dan Hoey?) posted some useful hacks a few months ago, including
an absolutely wonderful way to make the initial and final permutations
almost painless using a modification of a HAKMEM algorithm by Rick
Gumpertz and himself.  These used very fancy shifting and logical ops
to do the IP and FP in much less time than the table-lookup stuff that
I described briefly above (which still would need to be used for the
combined S-P operation).

	Jim Gillogly
-- 
	Jim Gillogly
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