An analysis of the CAST-256 cipher

We examine the cryptographic security of the CAST-256 symmetric block encryption algorithm. The CAST-256 cipher has been proposed as a candidate for the Advanced Encryption Standard currently under consideration by the U.S. National Institute of Standards and Technology (NTST). It has been designed for a 128-bit block size and variable key sizes of up to 256 bits to suit AES requirements. We specifically consider the cryptographic security of the cipher in relation to the cryptanalytic property of diffusion and the cryptanalysis techniques of linear and differential cryptanalysis.