A Novel Method to Increase Diffusion and Confusion in AES Algorithm

Abstract

The Advanced Encryption Standard (AES) is the most famous amongst symmetric block cipher algorithms, and the most used one in many different applications, because its encryption strength and its resistance to many attacks. In this paper, a novel approach will be introduced to remove some weakness points in AES and increase its security. Unlike most previous researches, this research will improve the most important and powerful part of AES algorithm which is the MixColumns() transformation. In the original AES, there only one function is used, which it creates a fixed array that is used in MixColumns() transformation, and this fixed array is known by attackers. Alternatively, the expanded secret key will be used to generate a different function at each round of AES. These functions will create a variable dynamic arrays at each round based on expanded secret key. The variable dynamic arrays will increase confusion amongst bits of the encrypted text. After that, the ShiftRow() transformation will be complicated from ShiftRow() with fixed pattern to ShiftRowColumn() with variable dynamic pattern according to expanded secret key. The modified ShiftRowColumn() will increase the diffusion amongst bytes of encrypted text, as will be detailed in experimental results.