**caesar** - decrypt caesar ciphers

**caesar** [*rotation*]

**caesar** attempts to decrypt caesar ciphers using English letter
frequency statistics. **caesar** reads from standard input and writes
to standard output.

If the optional numeric argument *rotation* is used, **caesar** will
rotate by that many letters. Otherwise **caesar** will try all 26
possible rotations and choose whichever seems most likely according to
the frequency statistics.

Caesar ciphers involve rotating the letters in the input through the alphabet by a specified number. The original cipher, devised by Julius Caesar, involved a rotation of three letters; A becomes D, B becomes E, C becomes F, etc. A 13-letter rotation is often used in newsgroup postings.

The frequencies used in this implementation are:

E 12.37, T 9.68, S 8.77, A 7.97, O 6.96, R 6.63, I 6.39, N 5.92, D 4.78, H 4.49, L 3.81, C 3.61, P 2.91, M 2.69, U 2.62, Y 2.07, F 2.01, W 1.88, G 1.46, B 1.35, V 0.81, K 0.42, X 0.23, Q 0.08, Z 0.06, J 0.04

This implementation of **caesar** has no known bugs.

This implementation of **caesar** in Perl was written by Ronald J
Kimball, *rjk-perl@tamias.net*. Based on caesar.c from the NetBSD
games distribution, by Stan King and John Eldridge, which was based on
an algorithm suggested by Bob Morris.

$Log: caesar.ppt,v $ Revision 1.2 2003/06/05 03:40:07 rjk minor improvements new email address

Revision 1.1 2000/01/07 21:56:27 rjk Initial revision

This program is copyright 2000 by Ronald J Kimball.

This program is free and open software. You may use, modify, or distribute this program (and any modified variants) in any way you wish, provided you do not restrict others from doing the same.