outer@utcsri.UUCP (Richard Outerbridge) (03/09/85)
In January's CRYPTOLOGIA, Robert Scott presents ("Wide-Open Design
Offers Flexible Implementations") an algorithm for a very simple
Feistel cipher, which he suggests is appropriate (for example) for
use with "...small operating systems..." that currently use
simulations of WW 2 rotor machines (anyone we know?).
The algorithm ("NEWDES") uses one 8-bit (256 byte) "S"-box, derived
by pseudo-random permutation keyed from the American Declaration of
Independence. It uses 17 rounds, thus avoiding the final swap
(or non-swap) of block halves; 15 bytes (120 bits) of key, 7 of which
are used every two rounds; a one byte circular shift every second round
instead of permutations; and key-interrupting text feedback to overcome
the problems of degenerate and symetrical keys. It runs VERY quickly.
Key and text diffusion is much slower than the DES, and he didn't do
any correlation tests.
Obviously this is less complex than the DES. Any opinions whether it's
less robust than crypt(1)?
--
Richard Outerbridge <outer@utcsri.UUCP> (416) 961-4757
Payload Deliveries: N 41 39'36", W 79 23'42", Elev. 106.47m.