Higher Order Differential Attack on the Lightweight Block Cipher LBC-3

LBC-3 is the lightweight block cipher proposed by Nyssanbayeva et al. in 2022. The block size is 64 bits, the secret key size is 80 bits, and the number of rounds is 20, respectively. The designer investigated the avalanche effect of LBC-3, and Yasushi et al. evaluated the security against differential and linear cryptanalysis. Meanwhile, the security against higher order differential cryptanalysis, one of the most powerful attacks on block cipher, has not been evaluated. In this paper, we evaluated the security of LBC-3 by applying a higher order differential attack. By computer experiments, we discovered the 12-round characteristic using the 28-th order differential. We clarified the reason for this characteristic through a detailed analysis of the nibble values. Then, by using the 60-th order differential, we also show the 18-round characteristic, which is a 6-round extension of the 12-round one theoretically. Exploiting the 18- round characteristic, it is possible to apply the higher order differential attack to full-round LBC-3 with 2⁶¹'⁶ data and times of encryption.