Zero-Correlation Linear Cryptanalysis of Reduced-Round LBlock
Zero-correlation linear attack is a new method for cryptanalysis of block ciphers developed by Bogdanov et al. in 2012. In this paper, the authors adapt the matrix method to find zero-correlation linear approximations. Then they present several zero-correlation linear approximations for 14 rounds of LBlock and describe a cryptanalysis for 22 rounds of the reduced LBlock. After biclique attacks on LBlock revealed weaknesses in its key schedule, its designers presented a new version of the cipher with a revised key schedule. The attack presented in this paper is applicable to LBlock structure independently of the key scheduling. The attack needs distinct known plaintexts which are more realistic attack model in comparison with impossible differential cryptanalysis which uses chosen plaintext pairs.