Enhanced Key Expansion for AES-256 by using Even-Odd method

This study is conducted to determine an alternative, creative method for designing Key Expansion in AES-256 that is called Even-Odd (E-O) method. The proposed algorithm consists of two parts. The first part is Key Expansion and the second part is E-O Select Round Key. The cipher key is 256 bits as an input and the output is fifteen round keys that are 128 bits and include 14 round keys and one pre round key. The element of confusion is highly being concerned in this algorithm and efficiency is improved compared to the classic existing algorithms. The avalanche effect of E-O method is highly improved than classic method. In addition, the concept of weak key is eliminated from the mentioned algorithm. The results also show that the performance of the sub-keys generation is equivalent to the classic AES algorithm.