Caesar cipher (also referred to as Caesar algorithm, Caesar shift, shift cipher, or as Simple Caesar) is a simple symmetric encryption method based on monographic and monoalphabetic substitution.

In encryption, each letter of the plaintext is mapped to a ciphertext letter. This mapping is obtained by cyclically shifting (rotating) the characters of an ordered alphabet to the right by a certain number; cyclic means that when shifting beyond Z, one continues counting again starting at A. The number of characters shifted forms the ciphertext letter. The number of shifted characters forms the key, which remains unchanged for the entire encryption.