1.\" Copyright (c) 1989, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)caesar.6 8.2 (Berkeley) 11/16/93 29.\" 30.Dd November 16, 1993 31.Dt CAESAR 6 32.Os 33.Sh NAME 34.Nm caesar , rot13 35.Nd decrypt caesar ciphers 36.Sh SYNOPSIS 37.Nm 38.Op Ar rotation 39.Nm rot13 40.Sh DESCRIPTION 41The 42.Nm 43utility attempts to decrypt caesar ciphers using English letter frequency 44statistics. 45.Nm Caesar 46reads from the standard input and writes to the standard output. 47.Pp 48The optional numerical argument 49.Ar rotation 50may be used to specify a specific rotation value. 51If invoked as 52.Nm rot13 , 53a rotation value of 13 will be used. 54.Pp 55The frequency (from most common to least) of English letters is as follows: 56.Bd -ragged -offset indent 57ETAONRISHDLFCMUGPYWBVKXJQZ 58.Ed 59.Pp 60Their frequencies as a percentage are as follows: 61.Bd -ragged -offset indent 62E(13), T(10.5), A(8.1), O(7.9), N(7.1), R(6.8), I(6.3), S(6.1), H(5.2), 63D(3.8), L(3.4), F(2.9), C(2.7), M(2.5), U(2.4), G(2), 64P(1.9), Y(1.9), 65W(1.5), B(1.4), V(.9), K(.4), X(.15), J(.13), Q(.11), Z(.07). 66.Ed 67.Pp 68Rotated postings to 69.Tn USENET 70and some of the databases used by the 71.Xr fortune 6 72program are rotated by 13 characters. 73