# Implementing Homomorphic Encryption Based Secure Feedback Control for Physical Systems

## TL;DR

This paper presents a method for implementing secure feedback control of physical systems using homomorphic encryption, enabling privacy-preserving control laws with FPGA implementation and experimental validation on an inverted pendulum.

## Contribution

It introduces a homomorphic encryption-based approach for secure linear control implementation, including PID controllers, suitable for FPGA realization and real-time unstable system control.

## Key findings

- Feasible FPGA implementation of encrypted control laws
- Timing and resource analysis for different key lengths
- Successful control of an unstable inverted pendulum

## Abstract

This paper is about an encryption based approach to the secure implementation of feedback controllers for physical systems. Specifically, Paillier's homomorphic encryption is used to digitally implement a class of linear dynamic controllers, which includes the commonplace static gain and PID type feedback control laws as special cases. The developed implementation is amenable to Field Programmable Gate Array (FPGA) realization. Experimental results, including timing analysis and resource usage characteristics for different encryption key lengths, are presented for the realization of an inverted pendulum controller; as this is an unstable plant, the control is necessarily fast.