____________________________________________________________________
If the law is based on precedence, why is the Constitution
not the final precedence since it's the primary authority?
The Armadillo Group ,::////;::-. James Choate
Austin, Tx /:'///// ``::>/|/ ravage@ssz.com
www.ssz.com .', |||| `/( e\ 512-451-7087
-====~~mm-'`-```-mm --'-
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---------- Forwarded message ----------
Date: Tue, 20 Mar 2001 12:49:02 +1100
From: Greg Rose
To: coderpunks@toad.com
Subject: a 32-bit block cipher
Recently I needed a way of generating an
unpredictable permutation function of 32-bit
values, in other words, a block cipher with a
32-bit block. It was important for that
application that 32-bit values generated over a
period of time should not repeat. I searched
around looking for such a cipher, and couldn't
find one, not surprisingly since it would be
insecure in the face of a codebook style attack
(the entire codebook would fit into 16GB).
Anyway, that didn't change the fact that I needed
one, so I wrote one. I took Skipjack (Panu
Rissanen 's version) and turned it
into a 24-round feistel cipher. It retains the
F-table, the G-permutation and the key-schedule
(including the 80-bit keys), but it loses the
feedback register structure and the two different
kinds of rounds.
Then for the fun of it I applied for, and
received, an export license from the Australian
Defence Signals Directorate that allows me to post
it on the Web. It's at:
http://www.home.aone.net.au/qualcomm/skip32.c
It's freely available, and I hope it is of use to
someone else too. If anyone sees any problems with
it, please do tell me.
Greg.
Greg Rose INTERNET: ggr@qualcomm.com
Qualcomm Australia VOICE: +61-2-9817 4188 FAX: +61-2-9817 5199
Level 3, 230 Victoria Road, http://people.qualcomm.com/ggr/
Gladesville NSW 2111 232B EC8F 44C6 C853 D68F E107 E6BF CD2F 1081 A37C
