A simple form of encryption in which each letter in the plaintext is shifted through the alphabet a number of positions (for example A→D, B→E, C→F, etc.).

A manual symmetric encryption technique that encrypts pairs of letters (digraphs).

(cryptography) a symmetric-key cipher in which plaintext digits are combined with a pseudorandom cipher digit stream

(cryptography) A symmetric structure used in the construction of block ciphers. It is an iterated cipher with an internal function called a round function.