A probabilistic correlation attack on the shrinking generator

Abstract

A probabilistic correlation attack on irregularly clocked shift registers is applied in a divide and conquer attack on the shrinking generator. Systematic computer simulations show that the joint probability is a suitable basis for the correlation attack and that, given a keystream segment of length linear in the length of the clock-controlled shift register, the shift register initial states can be identified with high probability. The attack is conducted under the assumption that the secret key controls only the shift register initial states.