FARRAH FAREED2025-10-282025-10-282022https://escholar.umt.edu.pk/handle/123456789/9629Nowadays, many organizations, companies, and an individual person share their data online through unreliable mediums ignoring that there are many hackers sitting outside to hack their data and misuse it. A cipher in cryptography is a set of predetermined procedures that may be used as a technique to achieve encryption and decryption. Cryptosystems are employed to demonstrate the security of private communication and information networks. Various permutation and substitution techniques are employed for this purpose. S-Box is in charge of the substitution procedure. Modern ciphers employ dynamic, key-dependent S-Box. In this work, we suggested a way for creating dynamic S-Boxes with strong cryptographic features. Techniques, such as bijectivity, nonlinearity, strict avalanche criteria, and linear probability, are used to assess the strength of the S-Box. After the creation of a dynamic S-Box, it is used in a novel cipher designed in this research thesis. Novel cipher consists of three phases such as key generation, encryption, and decryption. A different S-Box is generated using values taken from the key and employed in a cipher round to make things more difficult for the attackers.enThesis