Linear Cryptanalysis of the SAFER Block Cipher Family

This paper presents a linear cryptanalytic attack against the SAFER family of block ciphers. Linear cryptanalysis is a statistical well-known-plaintext attack that explores (approximate) linear relations between plaintext, ciphertext and subkey bits. These linear relations apply only to certain key classes. The results show that by considering nonhomomorphic linear relations, more rounds of the SAFER block cipher family can be attacked. The new attacks pose no threat to any member of the SAFER family.