NAME
caesar, rot13
— decrypt caesar
cyphers
SYNOPSIS
caesar |
[rotation] |
rot13 |
DESCRIPTION
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:
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).