Caesar Cipher Algorithm

The Caesar cipher is one of the simplest and best known encryption algorithms, a substitution cipher that shifts every letter of a message forward by a fixed number of positions in the alphabet. Encryption and decryption both amount to simple arithmetic on letter positions: shifting by three, for example, turns every D into an A and every E into a B, wrapping back around to the start of the alphabet as needed. The cipher takes its name from Julius Caesar, who, according to the Roman historian Suetonius, used a shift of three to protect messages of military importance, making his the earliest well-documented use of the technique even though simpler substitution ciphers likely existed before him. Because English has only twenty five possible non-zero shifts, an attacker can simply try every one of them, and even without that shortcut the uneven frequency of letters in ordinary text makes the shift easy to recover through frequency analysis, so the cipher offers essentially no real protection today.