Variations to S-box and MixColumn Transformations of AES

Variations to S-box and MixColumn transformations of Rijndael are discussed in this paper. These variations are designed over the Galois field GF(2) generated by the primitive polynomial x + x + x + x + 1. The proposed S-box is constructed by computing the powers of a primitive root in F257 and taking the multiplicative inverse of the resulting entries as in Rijndael’s algorithm. The new MixColumn transformation has self-inverse and uses the coefficients 01, 02, and 03. Hence it improves the performance of the inverse cipher and also reduces the complexity of the system that supports the inverse cipher. As a trade-off this transformation has relatively low relevant diffusion power.