# Cipher

81

**cipher square**— noun : vigenère tableau …82

**Vigenère cipher**— The Vigenère cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. It is a simple form of polyalphabetic substitution.The Vigenère (pronEng|ˌviːdʒɪˈnɛəɹ, veedj ih nair )… …83

**Substitution cipher**— In cryptography, a substitution cipher is a method of encryption by which units of plaintext are replaced with ciphertext according to a regular system; the units may be single letters (the most common), pairs of letters, triplets of letters,… …84

**Caesar cipher**— The action of a Caesar cipher is to replace each plaintext letter with one fixed number of places down the alphabet. This example is with a shift of three, so that a B in the p …85

**Block cipher modes of operation**— This article is about cryptography. For method of operating , see modus operandi. In cryptography, modes of operation is the procedure of enabling the repeated and secure use of a block cipher under a single key.[1][2] A block cipher by itself… …86

**Classical cipher**— A cipher is a means of concealing a message, where letters of the message are substituted or transposed for other letters, letter pairs, and sometimes for many letters. In cryptography, a classical cipher is a type of cipher that was used… …87

**Stream cipher**— The operation of the keystream generator in A5/1, a LFSR based stream cipher used to encrypt mobile phone conversations. In cryptography, a stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher… …88

**Hill cipher**— Hill s cipher machine, from figure 4 of the patent In classical cryptography, the Hill cipher is a polygraphic substitution cipher based on linear algebra. Invented by Lester S. Hill in 1929, it was the first polygraphic cipher in which it was… …89

**Transposition cipher**— In cryptography, a transposition cipher is a method of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the ciphertext… …90

**Block cipher**— In cryptography, a block cipher is a symmetric key cipher operating on fixed length groups of bits, called blocks, with an unvarying transformation. A block cipher encryption algorithm might take (for example) a 128 bit block of plaintext as… …