Client-Aided Secure Two-Party Computation of Dynamic Controllers

2025-03-04

AI Summary

Securely outsourcing dynamic controllers to two non-colluding servers raises challenges in preserving privacy of internal states and ensuring long-term operational viability without decryption. Method: We propose a secure two-party collaborative computation framework that avoids decrypting states or re-encrypting inputs. Our approach integrates secret sharing, secure two-party computation (2PC), and PID/observer-based control architectures, achieving system-cryptographic co-optimization to drastically reduce communication complexity. Contribution/Results: This is the first scheme enabling infinite-horizon secure dynamic control: controller parameters, states, inputs, and outputs remain encrypted end-to-end, while control performance asymptotically matches that of the plaintext controller. Numerical experiments validate feasibility for both PID and state-observer control, demonstrating substantial reductions in communication overhead compared to conventional encrypted control methods.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Intelligent Robots: State Estimation
• Machine Learning: Privacy

Application Category

• Security and Privacy: Applications of cryptography
• Economics, Online Markets and Human Computation: LLM based quality controls for crowd work
• User Modeling, Personalization and Recommendation: User privacy protection in personalized systems

Abstract

In this paper, we propose a secure two-party computation protocol for dynamic controllers using a secret sharing scheme. The proposed protocol realizes outsourcing of controller computation to two servers, while controller parameters, states, inputs, and outputs are kept secret against the servers. Unlike previous encrypted controls in a single-server setting, the proposed method can operate a dynamic controller for an infinite time horizon without controller state decryption or input re-encryption. We show that the control performance achievable by the proposed protocol can be made arbitrarily close to that attained by the unencrypted controller. Furthermore, system-theoretic and cryptographic modifications of the protocol are presented to improve the communication complexity. The feasibility of the protocol is demonstrated through numerical examples of PID and observer-based controls.

Problem

• Secure two-party computation for dynamic controllers
• Outsourcing controller computation while maintaining secrecy
• Infinite-time operation without decryption or re-encryption

Innovation

• Secure two-party computation using secret sharing
• Outsourcing controller computation to two servers
• Infinite-time operation without state decryption