An Approach to Encrypted Fault Detection of Cyber-Physical Systems

The networking of Cyber-Physical Systems (CPS) is a worldwide trend. With the growing accessibility of data vulnerability to attacks increases. Recent cyber attacks like Triton point out the necessity of new methods to secure CPS. Despite multiple dissimilarities between CPS and a general IT system, the mature field of IT security can inspire new methods for the protection of CPS such as cryptography. The encryption of signals transferring through the network is not new. The homomorphic encryption scheme allows execution of mathematical operations in the encrypted domain. This allows to encrypt not only signals in the network but also parameters and variables of a remote monitoring system. In this way, it is much more difficult for the adversary to gather information about the plant to execute a stealthy attack. In this paper, a somewhat homomorphic encryption scheme is applied to a CPS to ensure safe and secure communication by protecting all signals and variables in the network without loss of performance. A numerical example demonstrates the security level that can be achieved by applying this scheme.