Square (cipher)

Square is a block cipher designed by Joan Daemen and Vincent Rijmen, who later designed Rijndael, the winning candidate in the AES competition. Like AES, Square is a substitution-permutation network operating on 128-bit blocks. It gets it name from the fact that, like AES, for some operations it treats the block as a four-by-four square array of bytes. It uses eight rounds and a 128-bit key.

Lars Knudsen invented a new attack, called integral cryptanalysis or the square attack, to break Square. It was published at the same time as the cipher itself.