ENClose: Encrypted Nonlinear Closed-Loop Control Over Fully Homomorphic Encryption

This research proposes ENClose, a framework that lets control systems (automated systems that adjust themselves based on feedback) operate securely using fully homomorphic encryption, or FHE, a cryptographic method that keeps data encrypted while performing calculations on it. The main innovation addresses two problems: noise building up in encrypted feedback loops and the slowness of doing complex nonlinear operations (calculations that don't follow straight-line relationships) on encrypted data. ENClose uses techniques like function segmentation and tree-based selection to speed up these encrypted calculations by 3 to 20 times compared to previous methods, as demonstrated in real-world tests like vehicle formation control and anomaly recovery.