We examine diffusion properties of Rijndael which has been selected by US National Institute of Standards and Technology (NIST) for the proposed Advanced Encryption Standard (AES). Since the s-box of Rijndael applies a nonlinear transformation operating on each byte of the intermediate cipher result independently, its characteristics have significant effects on the strength of the entire system. The characteristics of Rijndael’s s-box are investigated for the criteria of avalanche, strict avalanche, bit independence, nonlinearity and XOR table distribution. We also evaluate the overall performance for different rounds of Rijndael, and compare it to Safer K-64, in terms of Avalanche Weight Distribution (AWD) criterion.
Selçuk Kavut, Melek D. Yücel