Breaking chaotic shift key communication via adaptive key identification

This paper proposes an adaptive parameter identification method for breaking chaotic shift key communication from thetransmitted signal in public channel. The sensitive dependenceproperty of chaos on parameter mismatch is used for chaos adaptivesynchronization and parameter identification. An index functionabout the synchronization error is defined and conjugate gradientmethod is used to minimize the index function and to search thetransmitter's parameter (key). By using proposed method, secure keyis recovered from transmitted signal generated by low dimensionalchaos and hyper chaos switching communication. Multi-parameters canalso be identified from the transmitted signal with noise.