A new higher order differential of LBlock

LBlock is a 64-bit block cipher proposed by Wu et al. in 2011. It has been reported that LBlock has a 15-round saturation characteristic, in which 16 bits of the output of 15-th round 60-th order differential equals to zero. By using this characteristic, a 20-round LBlock is attacked with 2^63.6 blocks of chosen plaintext and 2^39.6 times of data encryption. This paper shows a new higher order differential of LBlock. By computer experiment, we found eight kinds of new 10-round saturation characteristics, in which 24 bits of the output of 10-th round 12-th order differential equals to zero. These characteristics are extendable with 5-round, we also show eight kinds of new 15-round saturation characteristics using 60-th order differential. If we use it, it is possible to apply the higher order differential attack to 21-round LBlock with 2^63.6 blocks of chosen plaintext and 2^63.6 times of data encryption.