TMTO attacks on stream ciphers – theory and practice
Jan Krhovják, Jiří Kůr, Ondřej Šiler, Paul C. Leyland · 2011
This paper deals with issues related to a cryptanalytic time-memory trade-off (TMTO) attacks on stream ciphers. We describe the basic theory and principles of TMTO attacks and their practical application on selected stream ciphers – namely on A5/1 cipher that is used in GSM (Global System for Mobile communications) standard. We focus mainly on the pre-computation phase of TMTO attacks. This phase includes data pre-computation and construction of various types of Hellman or Rainbow tables. The goal of the pre-computation is to cover some percentage of the key space with specially constructed chains. Our results demonstrate the real impact of various table parameters and chain constructions and show a substantial difference between theory and practice.