Cube attack on Trivium and A5/1 stream ciphers

Abstract

Cube attack has been proposed by Dinur and Shamir in 2009. It is an addition in the area of cryptanalysis applicable to a wide range of symmetric key algorithms. Cryptographic schemes may be represented by tweakable polynomials in GF(2) in terms of secret and public variables. Cube attack is a major improvement over existing techniques used for solving such polynomial equations. In this research, stream ciphers Trivium and A5/1 have been analyzed against the cube attack. 69 out of 80 key bits for 576 round Trivium have been successfully recovered with a complexity of 212, 63 cipher evaluations. 20 linearly independent relations have been found for 5 round A5/1 with the attack complexity of 244 cipher iterations. Cube attack software toolkit from our previous research has been utilized for cube cryptanalysis.