caesar, rot13 - decrypt caesar ciphers
The caesar utility attempts to decrypt caesar ciphers 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.
The frequency (from most common to least) of English letters is as
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),
Rotated postings to USENET and some of the databases used by the
fortune(6) program are rotated by 13 characters.