Power-balancing software implementation to mitigate side-channel attacks without using look-up tables

With the increasing number of side-channel attacks, countermeasure designers continue to develop various implementations to address such threats. Power-balancing (PB) methods hold the number of 1s and/or transitions (i.e., Hamming weight/distance) of internal processes constant to ensure side-channel safety in an environment in which it is difficult to use random numbers. Most existing studies employed look-up tables (LUTs) to compute those operations, except for XOR and NOT operations. However, LUT-based schemes exhibit some side-channel issues in the address bits of LUTs. In this paper, we propose the application of AND and ADD operations to PB methods based on a rule that encodes 8-bit data into a 32-bit codeword without using LUTs. Unlike previous studies that employed LUTs, our proposals overcome side-channel vulnerabilities associated with the address bits and memory wastage. In addition, we evaluate the side-channel security ensured by the proposed method in comparison with that ensured by other methods. Finally, we apply our methods to SIMON/SPECK ciphers and analyze their performance by comparing them with older schemes.