Paper 2012/570 Original: eprint.iacr.org/2012/570 ↗

Zero-Correlation Linear Cryptanalysis of Reduced-Round LBlock

Abstract

Zero-correlation linear attack is a new method for cryptanalysis of block ciphers developed by Bogdanov et al. in 2012. In this paper we adapt the matrix method to find zero-correlation linear approximations. Then we 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 is a more realistic attack model in comparison with impossible differential cryptanalysis which uses chosen plaintext pairs. Moreover, we performed simulations on a small variant LBlock and present the first experimental results on the theoretical model of the multidimensional zero-correlation linear cryptanalysis method.