CAESAR(6)                     System Games Manual                    CAESAR(6)

NAME
     caesar , rot13 - decrypt caesar cyphers

SYNOPSIS
     caesar [rotation]
     rot13

DESCRIPTION
     The caesar utility attempts to decrypt caesar cyphers using English let-
     ter frequency statistics.  caesar reads from the standard input and
     writes to the standard output.

     The optional numerical argument rotation may be used to specify a spe-
     cific rotation value. When caesar is invoked as rot13 this is the same as
     a rotation of 13.

     The frequency (from most common to least) of English letters is as fol-
     lows:

           ETAONRISHDLFCMUGPYWBVKXJQZ

     Their frequencies as a percentage are as follows:

           E(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),  D(3.8),  L(3.4),  F(2.9),  C(2.7),  M(2.5),  U(2.4), G(2),
           P(1.9), Y(1.9),  W(1.5),  B(1.4),  V(.9),  K(.4),  X(.15),  J(.13),
           Q(.11), Z(.07).

     Rotated postings to USENET and some of the databases used by the
     fortune(6) program are rotated by 13 characters (aka "rot13").

BSD                              June 4, 2004                              BSD