ABDUL MUQEET2025-09-292025-09-292021https://escholar.umt.edu.pk/handle/123456789/7311Cryptosystems are used to prove the security of confidential information and communication networks. For this purpose, various permutation and substitution processes are used. The process of substitution is performed by S-box. There are number of S-boxes that are developed but these are static or week so there is need to develop the strong and dynamic S-boxes. The modern day cipher use key dependent S-box that are dynamic. In this thesis the novel dynamic S-box is proposed. To determine the strength of proposed S-Box some standard tools are defined named as Bijectiveness, Nonlinearity, Strict Avalanche Criterion, Linear Probability, and Differential Uniformity. The results are compared with existing S-boxes.enThesis