Extending the Resynchronization Attack

Synchronous stream ciphers need perfect synchronization between sender and receiver. In practice, this is ensured by a resync mechanism. Daemen et al. [10] first described attacks on ciphers using such a resync mechanism. In this paper, we extend their attacks in several ways by combining the standard attack with cryptanalytic techniques such as algebraic attacks and linear cryptanalysis. Our results show that using linear resync mechanisms should be avoided, and provide lower bounds for the nonlinearity required from a secure resync mechanism.