Improved S-box Based on Strict Avalanche Distance Criterion

The S-box is the only nonlinear part of the AES algorithm. Its essence is a multi-output Boolean function composed of several component functions. Its main purpose is to confuse the realization of nonlinearity and pseudo-randomness. In this paper the algebraic properties and the construction principle of S-box have been analyzed. A new approach has been used to screen the transformation of the S-box, and the new affine pair reduced the strict avalanche criterion distance of the S-box. The improved S-box was compared with the S-box of the AES algorithm and the S-box constructed in the literature1. The new S-box has a good algebraic property and is closer to the strict avalanche criterion.