Impossible differential cryptanalysis of LBlock through breaking down the key space

Impossible differential cryptanalysis is a serious threat against block ciphers. In this paper, we represent a new method for impossible differential cryptanalysis of LBlock through breaking down the target key space into independent subspaces, and extending the results of searches to the main target key space. We apply the new method on 22 rounds of LBlock. The represented attack requires 2⁶³ chosen plaintexts and the time complexity is equivalent to 2^72.5 encryptions.