Caesar's cipher

In this cipher, the alphabet is the usual alphabet of Roman letters. Punctuation, spaces and capitalizations are ignored. It is reported that Caesar used an encryption based on the substitution A d, ... , Z c, given by the table below.

 A B C D E F G H I J K L M d e f g h i j k l m n o p

 N O P Q R S T U V W X Y Z q r s t u v w x y z a b c

Example 1.7.22   Go Tigers'' is enciphered as jr wljhuv''.

If we identify each letter with its corresponding number via the labeling is , is , ..., is , then Caesar's cipher is a cipher for which any letter is related to its enciphered letter by

where in the example above . More generally, a substitution cipher is a cipher for which the alphabet has been rearranged according to some fixed permutation. The Caesar cipher is a special case of this where the permutation is as indicated above.

David Joyner 2007-09-03