Abstract
Substitution box is a significant and only nonlinear constituent of block cipher. S-box plays a central role in converting the intelligible message or plain text, into an enciphered format. Construction of strong S-boxes is an important area of interest for security experts. In this work, we develop a new method to evolve S-boxes with the help of coset graph for the action of PSL(2, Z) on projective line over the finite field GF (2(8)), a special type of bijective map g and the symmetric group S-256 The capability of the proposed S-boxes to mitigate cryptanalysis is investigated through various performance analyzing parameters. The outcomes of the comparison with the familiar S-boxes indicate that the working abilities of newly designed S-boxes are better than that of many of the well-known S-boxes.