Attack detection method for encrypted wave-variable-based bilateral control systems

This study presents an energy-based attack detection method involving an encrypted bilateral control system using wave variables. In the considered bilateral control system, the leader and follower receive the follower's force information and the leader's velocity information, respectively, through the wave variables. The considered attack model multiplies the wave variables by an attack parameter, which is possible due to the malleability of the encryption scheme. The bilateral control system will be destabilized if the attacker chooses a relatively large parameter value. This motivates in developing a passivity observer for each leader and follower side to compute the total energy and constructing an energy-based detection method that can be incorporated into the encrypted bilateral control system and is summarized in the presented theorem. Furthermore, this study provides a specific design for reasonable threshold parameters concerning the control system energy. The theorem and the experimental validation confirm that the developed encrypted wave-variable-based bilateral control system with the proposed attack detector is secure and effective as a countermeasure against malleability-based attacks.