Side-Channel Analysis of MAC-Keccak

NIST recently completed the SHA-3 competition with the selection of Keccak as the new standard for cryptographic hashing. In this paper, we present a comprehensive SideChannel Analysis of Keccak, when it is used with a secret key to generate a Message Authentication Code (MAC) (MAC-Keccak). Our analysis covers all the variations of the algorithm. We show that the side-channel resistance of the MAC-Keccak depends on the key-length used, and we derive the optimum key-length as ((n * rate) -1), where (n is an element of [2 : infinity) and rate is the Keccak input block size. Finally, the paper demonstrates the feasibility of our side-channel analysis with a practical attack against MACKeccak implemented on a 32-bit Microblaze processor.