Detection and Cancellation of Multiplicative FDI Attack on Bilateral Encrypted Control System

Teleoperation of remote assist robots has recently advanced owing to the development of communication technology. However, anonymous malicious attacks may intercept or falsify the network control system. Therefore it is necessary to improve the security against cyber-attacks. As a countermeasure, an encrypted control method has been applied to prevent intercepting and detect the falsification of control parameters, as well as control signals by performing control operations with encrypted signals and parameters. However, it is difficult to detect False Data Injection (FDI) attacks, which exploit encryption malleability, and countermeasures against such attacks are necessary. Therefore, this study proposes a novel method to detect and cancel the effect of the FDI attack, which aims at the encrypted bilateral control system’s malleability. The assumed FDI attack falsifies the plaintext by multiplying a constant factor, which is realized by monitoring the entire system’s energy change and estimating the attack parameters. The proposed method can detect and cancel the impact of the FDI attack within finite steps. Moreover, we verified the proposed method for the bilateral control system using ElGamal encryption and experimentally confirmed its effectiveness against the FDI attack.