CAESAR(6) Games Manual CAESAR(6)

caesar, rot13decrypt caesar cyphers

caesar [rotation]


The caesar utility attempts to decrypt caesar cyphers using English letter 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 specific rotation value.

If this utility is invoked as rot13, it will rotate by 13 characters. This format is commonly used on USENET and in some of the databases used by the fortune(6) program to “disguise” their content.

The frequency (from most common to least) of English letters is as follows:


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).
January 15, 2015 OpenBSD 7.5