On a Formalized Approach to Truncated Differential Cryptanalysis of Block Ciphers

Abstract

We propose a formalized approach to truncated differential cryptanalysis based on ternary masks which separately consider unchanged, obligatory changed and unknown bits in differences. We propose a security parameter for S-boxes and encryption mappings which bounds the probability of truncated differentials from below, and study its basic algebraic properties. Our approach allows to adapt existing techniques for mount classical differential attacks to truncated differential cryptanalysis, to extract more information from encryption process and to evaluate the complexity of truncated differential attacks.