Abstract: A fault attack on the self-shrinking generator is presented by changing the internal states in the linear feedback shift registers. Besides, a shifts attack on the shrinking generator is described by modifying the control clock. Results show that, for the shrinking generator, the attacker can obtain the secret keys by implementing n=max{n₁，n₂}times phase shift attacks, and that for the self-shrinking generator, the attacker can obtain the secret keys by changing the bit values in n registers.

Key words: fault analysis, self-shrinking generator, shrinking generator