A New Higher Order Differential of LCB

LCB is a 32-bit block cipher proposed by Roy et al. in 2021. The designers evaluated its security against differential cryptanalysis, linear cryptanalysis, and so on. On the other hand, it has not been reported the security of LCB against higher order differential cryptanalysis, which is one of the algebraic attacks. In this paper, we applied higher order differential cryptanalysis to LCB. Consequently, we found a new full-round higher order differential characteristic of LCB using 1-st order differential. Exploiting this characteristic, it is possible to apply the distinguishing attack to full-round LCB with 2 chosen plaintexts. Then, we also show that LCB can be broken under the condition for known plaintext attacks. Furthermore, we tried to improve the round function of LCB to analysis this vulnerability.