1. A method of converting data between an unencrypted format and an encrypted format, wherein said data are organised in bit words, the method including a plurality of rounds, each round being comprised of fixed set of transformations applied to a two-dimensional array, designated the state, of rows and columns of bit words, the method including the step of applying at least a part of said fixed set of transformations to a transposed version of said state, wherein said rows and columns are transposed for the columns and the rows, respectively.