Encrypted Control Systems with Fully Homomorphic Encryption

In order to improve cyber security, encrypted control systems have attracted much attention recently. Homomorphic encryption allows calculations to be performed directly based on ciphertexts. Especially by means of fully homomorphic encryption (FHE) schemes both signals transmitted over the network and controller parameters can be encrypted. This paper gives a brief overview of some prevalent FHE schemes as well as their applications in the control field. The focus will be put on the Brakerski/Fan-Vaikuntanathan (BFV) scheme, the Cheon-Kim-Kim-Song (CKKS) scheme and the Gentry-Sahai-Waters (GSW) scheme. A simulation study with the quadruple-tank system illustrates the FHE encrypted control systems and the computational aspects.