The saturation attack—a bait for Twofish
S Lucks - International Workshop on Fast Software Encryption, 2001 - Springer
S Lucks
International Workshop on Fast Software Encryption, 2001•SpringerThis paper introduces the notion of a “saturation attack”. Consider a permutation p over w-bit
words. If p is applied to all 2 w disjoint words, the set of outputs is exactly the same as the set
of inputs. A saturation attack exploits this fact. The current paper applies saturation attacks
on reduced-round variants of the Twofish block cipher with up to seven rounds with full
whitening or eight rounds without whitening at the end (ie, half of the cipher). The attacks
take up to 2 127 chosen plaintexts (half of the codebook) and are 2–4 times faster than …
words. If p is applied to all 2 w disjoint words, the set of outputs is exactly the same as the set
of inputs. A saturation attack exploits this fact. The current paper applies saturation attacks
on reduced-round variants of the Twofish block cipher with up to seven rounds with full
whitening or eight rounds without whitening at the end (ie, half of the cipher). The attacks
take up to 2 127 chosen plaintexts (half of the codebook) and are 2–4 times faster than …
Abstract
This paper introduces the notion of a “saturation attack”. Consider a permutation p over w-bit words. If p is applied to all 2w disjoint words, the set of outputs is exactly the same as the set of inputs. A saturation attack exploits this fact. The current paper applies saturation attacks on reduced-round variants of the Twofish block cipher with up to seven rounds with full whitening or eight rounds without whitening at the end (i.e., half of the cipher). The attacks take up to 2127 chosen plaintexts (half of the codebook) and are 2–4 times faster than exhaustive search. The attacks are based on key-independent distinguishers for up to six rounds of Twofish, making extensive use of saturation properties.
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