UEC - The University of Electro-Communications

Encrypted Control: Cryptographic Approach to Secure Control Systems

The spread of IoT technologies has allowed various automatic control systems to connect through cyberspace in a sophisticated manner. In the near future, it will be essential for engineers to be able to select cybersecurity measures according to system status and specifications. Kogiso Laboratory at the Department of Mechanical Engineering and Intelligent Systems has been studying the emerging area of encrypted control, an expected cybersecurity measure for automatic control systems. Our research group found that specific public-key encryption methodologies can conceal the controller parameters and proposed the concept of encrypted control for the first time in the field of control engineering (IEEE CDC 2015). As one of the pioneers of this technology, we have worked to develop a computational framework, control-theoretic methods, and experimental systems for implementation and application of motion control systems.

The encrypted control provides the secure implementation of a digital controller and a control system configuration. It possesses three features. The primary feature is that not only the transmission signals but also the controller parameters in the control algorithm are encrypted. This feature enables the control algorithm that directly outputs control signals in ciphertext to use encrypted information such as controller parameters and feedback signals in the ciphertext. Furthermore, because the computation within the controller does not require any decryption processes, it is not necessary to store and manage secret keys at the controller side. This second feature helps reduce the cost of protecting secret keys from adversaries and provides reliable use of cloud and fog computing architectures for distributed control systems. The last feature is that the encrypted control can be used easily to construct a real-time attack detector against cyberattacks, such as parameter falsification and signal tampering by malicious users. Additionally, any degradation of control performance caused by encrypting the controllers can be avoided by adjusting a security parameter (key length) of public-key encryption schemes. 

Currently, our research group is actively conducting research activities to establish and disseminate the encrypted control as a security countermeasure technology for automatic control systems. We are also developing cryptographic and control-theoretic approaches to more secure control systems and fundamental use cases to innovate next-generation control technologies. Through this multidisciplinary research and development, we hope to contribute to the most secure and safest control technology in the world. Kogiso Laboratory welcomes enthusiastic researchers and students who wish to collaborate with and join our research group to exploit this secure control issue and realize a future in which we live safely and securely. 


Papers selected:

  1. K. Kogiso and T. Fujita: Cyber-security enhancement of networked control systems using homomorphic encryption, IEEE Conference on Decision and Control (CDC), pp. 6838-6843, 2015/12/15-12/18. [ieeexplore]

  2. T. Fujita, K. Sawada, K. Kogiso, S. Shin: Security enhancement of networked control systems with RSA public-key cryptosystem, Transactions of the Society of Instrument and Control Engineers, Vol. 51, No. 9, pp. 655-660, 2015. (in Japanese)   [15_EncryptedCtrlRSA.pdf] (T. Fujita recieved SICE Academic Encouragement Award.)

  3. T. Fujita and K. Kogiso: Encryption of controllers using ElGamal cryptosystem, Transactions of the Society of Instrument and Control Engineers, Vol. 51, No. 9, pp. 661-666, 2015. (in Japanese)   [15_EncryptedCtrl.pdf

  4. K. Kogiso: Upper-bound analysis of performance degradation in encrypted control system, American Control Conference (ACC), pp. 1250-1255, 2018/6/27-6/29. [ieeexplore]

  5. K. Kogiso, R. Baba, and M. Kusaka: Development and examination of encrypted control systems, IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM), pp. 1338-1343, 2018/7/9-7/12. [ieeexplore]

  6. R. Baba, K. Kogiso, and M. Kishida: Detection method of controller falsification attacks against encrypted control system, SICE Annual Conference, pp. 244-248, 2018/9/11-9/14.

  7. K. Teranishi, M. Kusaka, N. Shimada, J. Ueda, and K. Kogiso: Secure observer-based motion control based on controller encryption, American Control Conference (ACC), pp. 2978-2983, 2019/7/10-7/12. [ieeexplore] (K. Teranishi recieved ACC 2019 Student Travel Award Grant.)

  8. K. Teranishi and K. Kogiso: Control-theoretic approach to malleability cancellation by attacked signal normalization, 8th IFAC Workshop on Distributed Estimation and Control in Networked Systems, IFAC-PapersOnLine, Vol. 52, No. 20, pp. 297-302, 2019/9/16-9/17. [IFAC-PapersOnLine]

  9. K. Teranishi, N. Shimada, and K. Kogiso: Stability analysis and dynamic quantizer for controller encryption, IEEE Conference on Decision and Control (CDC), pp. 7184-7189, 2019/12/11-12/13. (invited session "Encrypted Control and Optimization") [ieeexplore]

  10. K. Teranishi, N. Shimada, and K. Kogiso: Development and examination of fog computing-based encrypted control system, IEEE Robotics and Automation Letters, Volume 5, Issue 3, pp. 4642-4648, July 2020. [ieeexplore]

  11. K. Teranishi, K. Kogiso, and J. Ueda: Encrypted feedback linearization and motion control for manipulator with somewhat homomorphic encryption, IEEE/ASME International Conference on Advanced Intelligent Mechatronics, pp. 613-618, 2020/7/6-7/10. [ieeexplore]

  12. K. Teranishi, N. Shimada, and K. Kogiso: Stability-guaranteed dynamic ElGamal cryptosystem for encrypted control systems, IET Control Theory & Applications, Volume 14, Issue 16, pp. 2242-2252, 2020. [doi] (K. Teranishi recieved Telecom System Technology Student Award 2021.)

  13. K. Teranishi and K. Kogiso: ElGamal-type encryption for optimal dynamic quantizer in encrypted control systems, SICE Journal of Control, Measurement, and System Integration, Volume 14, Issue 1, pp. 59-66, 2021. [doi] (2022 SICE Outstanding Paper Award)

  14. T. Shin, K. Teranishi, and K. Kogiso: Cyber-secure pneumatic actuator system equipped with encrypted controller and attack detectors, Advanced Robotics, Volume 36, Issue 9, pp. 438-449, 2022.
  15. K. Teranishi and K. Kogiso: Optimal controller and security parameter for encrypted control systems under least squares identification, IEEE Control Systems Letters (w/ CDC23 option), Volume 7, pp. 1482-1487, April 2023.

  16. K. Teranishi, T. Sadamoto, A. Chakrabortty, and K. Kogiso: Designing optimal key lengths and control laws for encrypted control systems based on sample identifying complexity and deciphering time, IEEE Transactions on Automatic Control, Volume 68, Issue 4, pp. 2183-2198, April 2023.

  17. M. Miyamoto, K. Teranishi, K. Emura, and K. Kogiso: Cybersecurity-enhanced encrypted control system using keyed-homomorphic public key encryption, IEEE Access, Volume 11, pp. 45749-45760, May 2023.

  18. K. Teranishi, T. Sadamoto, and K. Kogiso: Input-output history feedback controller for encrypted control with leveled fully homomorphic encryption, IEEE Transactions on Control of Network Systems, Volume ??, Issue ??, pp. ???-???, 2023. (Early Access)


Open Source Software:

We provide Python and MATLAB simulation codes of encrypted control. [download]