Security Analysis of AES and Enhancing its Security by Modifying S-Box with an Additional Byte

Secured and opportune transmission of data alwaysis a significant feature for any organization.Robust encryption techniques and algorithms always facilitate in augmenting secrecy, authentication and reliability of data.At present, Advanced Encryption Standard (AES) patronized by NIST is the most secure algorithm for escalating the confidentiality of data.This paper mainly focuses on an inclusive analysis related to the security of existing AES algorithm and aim to enhance the level security of this algorithm.Through some modification of existing AES algorithm by XORing an additional byte with s-box value, we have successfully increased the Time Security and Strict Avalanche Criterion.We have used random additional key for increasing security.Since this key is random, result of security measurement sometimes fluctuates.