A metaheuristic tabu search approach for internal state reconstruction of RC4 stream cipher

Because of its simplicity and speed, RC4 is one of the most widely used stream cipher. In this paper we advance a cryptanalytic attack based on Tabu search algorithm which tries to reconstruct the internal state of RC4. Our attack relies on the cryptanalytic algorithm presented by Knudsen et al. in [9], the tree representation of the output word Zt and the tree of general conditions presented by Tomaševic et al. in [21]. Although the results of analitical calculations are slightly better than those given in [9] and [21], the attack remains impractical due to the high complexity.