A New ShiftColumn Transformation : An Enhancement of Rijndael Key Scheduling

In this paper, we proposed a new approach for key scheduling algorithm which is an enhancement of the Rijndael key scheduling. This proposed algorithm was developed to improve the weaknesses that has in the Rijndael key schedule. The key schedule function in Rijndael block cipher did not receive the same amount of attention during design phase as the cipher components. Based on our research, there are several properties in key schedule that seemed to violate the design criteria, which was published by NIST, and this has led to many types of attack performed on Rijndael block cipher. Thus we proposed an approach called ShiftColumn, operates by shifting bit and the result will be shifted with different offsets. This transformation is added as the last function after the RCon function. Our new approach improves the security of the original Rijndael key scheduling, by enhancing the bit confusion and diffusion of the subkey, which is output that is produced from the key schedule transformation. The subkeys produced by the proposed approach have been proven to be a better result on both properties compared to the subkeys that were produced from Rijndael key scheduling transformation. Keywords-component; Rijndael; Key Schedule; Proposed Approach of Key Schedule; Cryptography; Security