Finding New Differential Characteristics on SPECK Family

SPECK is a family of lightweight block ciphers. While Sun et al.’s evaluation of SPECK’s differential characteristics was the most effective, it left room for further analysis over longer rounds. In this paper, we use a SAT-based search algorithm to analyze SPECK48, SPECK96, and SPECK128, presenting optimal differential characteristics up to 19, 15, and 11 rounds, respectively. We also explore the best characteristics up to 20 rounds for SPECK48, 18 rounds for SPECK96, and 20 rounds for SPECK128.