In
cryptography,
integral cryptanalysis is a
cryptanalytic attack that is particularly applicable to
block ciphers based on
substitution-permutation networks. It was originally designed by
Lars Knudsen as a dedicated attack against
Square, so it is commonly known as the
Square attack. It was also extended to a few other ciphers related to Square:
CRYPTON,
Rijndael, and
SHARK.
Stefan Lucks generalized the attack to what he called a
saturation attack and used it to attack
Twofish, which is not at all similar to Square, having a radically different
Feistel network structure. Forms of integral cryptanalysis have since been applied to a variety of ciphers, including
Hierocrypt,
IDEA,
Camellia,
Skipjack,
MISTY1, MISTY2,
SAFER++,
KHAZAD, and
FOX (now called
IDEA NXT).