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In cryptography, Twofish is a symmetric key block cipher with a block size of 128 bits and key sizes up to 256 bits. It was one of the five finalists of the AES contest, but was not selected for standardisation. Twofish is related to the earlier block cipher Blowfish.

Twofish's distinctive features are the use of pre-computed key-dependent S-boxes, and a relatively complex key schedule. Twofish borrows some elements from other designs; for example, the Pseudo-Hadamard Transform (PHT) from the SAFER family of ciphers. Twofish uses the same Feistel structure as DES.

On most software platforms Twofish is slightly slower than Rijndael (the chosen algorithm for AES) for 128-bit keyA key is a piece of information that controls the operation of a cryptography algorithm. In encryption, a key specifies the particular transformation of plaintext into ciphertext, or vice versa during decryption. Keys are also used in other cryptographics, but somewhat faster for 256-bit keys.

As of 2004, there is no known attack on Twofish more efficient than brute force key searchIn cryptanalysis, a brute force attack is a brute-force search of the 'key space' (i. all possible keys) in an attempt to recover the plaintext used to produce a particular ciphertext. Note that, in most cases, recovery of the plaintext in this way is not.



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Block ciphers



Block ciphers [ }|action=edit}} Edit }]
Algorithms: 3-Way | AES | Akelarre | Blowfish | Camellia | CAST-128 | CAST-256 | CMEA | DEAL | DES | DES-X | FEAL | FROG | G-DES | GOST | ICE | IDEA | Iraqi | KASUMI | KHAZAD | Khufu and Khafre | LOKI89/91 | LOKI97 | Lucifer | MacGuffin | Madryga | MAGENTA | MARS | MISTY1 | MMB | NewDES | RC2 | RC5 | RC6 | REDOC | Red Pike | S-1 | SAFER | SEED | Serpent | SHACAL | SHARK | Skipjack | Square | TEA | Triple DES | Twofish | XTEA
Design: Feistel network | Key schedule | Product cipher | S-box | SPN   Attacks: Brute force | Linear / Differential  cryptanalysis | Mod n | XSL   Standardisation: AES process | CRYPTREC | NESSIE   Misc: Avalanche effect | Block size | IV | Key size | Modes of operation | Piling-up lemma | Weak key



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