Serpent (cipher)
Serpent is a symmetric key block cipher which was a finalist in the Advanced Encryption Standard contest, where it came second to Rijndael. Serpent was designed by Ross Anderson, Eli Biham, and Lars Knudsen.Like other AES submissions, Serpent has a block size of 128 bits and supports a key size of 128, 192 or 256 bits. The cipher is a 32-round substitution-permutation network operating on a block of four 32-bit words. Each round uses 32 copies of the same 4-bit to 4-bit S-box. Serpent was designed so that all operations can be executed in parallel, using 32 1-bit slices. This maximises parallelism, but also makes use of the extensive cryptanalysis work performed on DES.
Serpent was widely viewed as taking a more conservative approach to security than the other AES finalists, opting for a larger security margin: the designers deemed 16 rounds to be sufficient against known types of attack, but specified 32 rounds as insurance against future discoveries in cryptanalysis.
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Block ciphers
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Design: Feistel network | Key schedule | Product cipher | S-box | SPN Attacks: Brute force | Linear / Differential cryptanalysis Standardisation: AES process | CRYPTREC | NESSIE Misc: Block size | IV | Key size | Modes of operation