Cryptographic Strength Evaluation of AES S-box Variants

Abstract

In recent years, researchers have constructed AES s-box variants by customising the values of the parameters in the equation of AES s-box. Strength of these s-box variants is evaluated against the cryptographic properties like avalanche effect, nonlinearity and bit independence criteria, however, there are other important cryptographic properties of s-box, which need to be evaluated before adopting the s-box. In this paper, all types of AES s-box variants are reproduced and evaluated against ten cryptographic properties. The results of five properties, differential and linear probability, nonlinearity, balance and algebraic degree remains the same for any s-box variant due to isomorphic equivalence nature of the variants; whereas, strict avalanche effect, bit independence criteria, correlation immunity, cyclic and fix-point properties showed different results for different s-box variant. Finally, the results are compared with the standard AES s-box and conclusion of overall security of s-box variants with respect to selected properties is conferred.