Design of a Modified Rijndael Algorithm Using 2D Rotations

Summary Rijmen and Daemen had proposed Rijndael algorithm for Advanced Encryption Standard (AES) in June 1998. It was accepted for commercial use due to its symmetric and parallel structure, well adapted to modern processors and its suitability to smart cards. Rijndael algorithm uses an iterated block cipher with a variable block length and a variable key length. The block length and the key length can be independently specified to 128, 192 or 256 bits. We are proposing a modification which we rotate the bytes using 2 Dimensional rotation of the block after Step 4, thereby increasing confusion-diffusion. The proposed scheme will have improved complexity that increases the security for a 128 and 256 bits block case without increase in the length of the key used.