Secure Supervisory Control of Discrete Event Systems using Homomorphic Encryption *

This paper addresses the critical challenge of securing Cyber-Physical Systems (CPSs) against passive communication attacks, specifically focusing on systems modeled as Discrete Event Systems (DES). We introduce a methodology, based on the Elliptic Curve ElGamal (EC-ElGamal), to protect the confidentiality of DES-based CPS using homomorphic encryption. Our approach employs the computational intractability of the Elliptic Curve Discrete Logarithm Problem (ECDLP) to fortify supervisory control systems operating over vulnerable communication channels. The work details the EC-ElGamal protocol, from key generation to encryption and decryption, emphasizing its direct adaptation for ensuring robust data confidentiality within distributed DES architectures. A practical example demonstrating the application of this methodology in a DES context is implemented and tested on an ESP32 microcontroller.