Abstract: Advanced Encryption Standard is a reliable cryptosystem which is used in many applications. It consists of four rounds and byte substitution is the major of those rounds. Procedure of this round is to substitute the values with the entries of Substitution-Box which is known as S-Box. Its entries are pre-computed and stored on lookup tables (ROMs) to avoid tedious real time computations. There also have possible chance of attacks (known & Side-channel) proposed due to direct storage of S-Box and it spoils the overall security of the cryptosystem. To protect against such vulnerabilities, tracking on the security of the S-Box is necessary. Existing system that provides such security to the S-Box has time and space complexities in storage and searching mechanism. Our objective is to propose an optimized system from all the existing along with the space and time complexity of direct S-Box.

Keywords: S-BOX, IS-BOX, PP-BOX, IPP-BOX, S-Box, IS-Box