Книга: S-Box: Cryptography, Symmetric-Key Algorithm, Block Cipher, Ciphertext, Claude Shannon, Confusion and Diffusion, Bit, Twofish, Key, Bruce Schneier, International Data Encryption Algorithm

High Quality Content by WIKIPEDIA articles! In cryptography, an S-Box (Substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext ? Shannon's property of confusion. In many cases, the S-Boxes are carefully chosen to resist cryptanalysis. In general, an S-Box takes some number of input bits, m, and transforms them into some number of output bits, n: an m?n S-Box can be implemented as a lookup table with 2m words of n bits each. Fixed tables are normally used, as in the Data Encryption Standard (DES), but in some ciphers the tables are generated dynamically from the key e.g. the Blowfish and the Twofish encryption algorithms.