ABTRACT Lately, the Rijndael algorithm has been standardized by the NIST as the Advanced Encryption Standard (AES). This makes AES an essential and necessary data-protection mechanism for federal agencies in the US and other countries. In AES, rotation occurs in key expansion, ciphering, and deciphering. Rotation is vital for confusion and diffusion, which play an important role in any cryptography technique. Confusion and diffusion make breaking the key complex and difficult. This paper studies the effect of reconfiguring the structure of AES, especially replacing constant rotation with variable rotation. The resulting twin cipher is called Dynamic Rotation for Advanced Encryption Standard (DRAES). DRAES with variable rotation increases the complexity of the algorithm, and thus, increases the time consumed for brute-force attacks. We measured the diffusion of AES and DRAES algorithms. DRAES reached acceptable level of diffusion faster than AES
