Thesis Open Access
Nigusu, Gebeyehu Zinabu
Encryption is a method of coding information or sensitive data or asset, to prevent unauthorized users from accessing it. Now a day, it is essential to secure data that is at rest in our computer or is transmitted via web against attacks. Several of cryptographic techniques are being used to preserve security and could be classified as: symmetric and asymmetric. A symmetric algorithm named as (AES) is selected for enhancement due to its applicability and widely used algorithm. In AES, among the four stages that are used for encryption and decryption Sub Bytes and Mix Column produce more delay; from the two, mix column accounts 60% of the whole delay. On the other side, Shift Rows stage contribute to less security level of AES because it uses easy operation that is linear in nature. To overcome these challenges, in the designed symmetrical cryptography algorithm shift row stage of AES is replaced by symmetrical transposition technique to advance security and mix column stage is replaced by bitwise reverse transposition technique to improve the sped efficiency of the existing AES algorithm. The simulation result of our Symmetrical Transposition technique has shown better security achievement, with greater than 50% avalanche effect and Bitwise Reverse Transposition technique resulted in better encryption speed and decryption sped time when compared with original AES: 112.48%, 128.953% and 122.9% encryption speed performance because of symmetrical transposition, bitwise reverse transposition and combination of both techniques (ESE-AES), respectively taking average of ten trials; 114.3%, 140.8% and 128.4% increased the throughput because of symmetrical transposition, bitwise reverse transposition and combination of both techniques (ESE-AES). Hence, our proposed Enhanced Security-Efficiency Advanced Encryption Standard (ESE-AES) has better security, encryption and decryption speed performance and throughput when compared to original Advance Encryption Standard (AES).