Cyber-security has become vital for modern networked control systems (NCS). In this paper, we propose that the emerging technology of quantum key distribution (QKD) can be applied to enhance the privacy and security of NCS up to an unbreakable level. QKD can continuously distribute random secret keys with much higher privacy between communication parties, and thus enable the one-time pad encryption that cannot be truly applied in classical networks. We show that the resulting overall security of NCS can be essentially improved, and present a composable definition of security based on the analysis of the key generation and management processes. Moreover, because the security is mainly determined by quantum keys rather than the complexity of encryption algorithms, the control performance can be improved as well by reducing the time delay using simpler algorithms. These advantages are demonstrated by the example of a remotely controlled servo system, showing that the introduction of QKD to NCS can simultaneously improve the security and performance by using the simplest encryption algorithm XOR. Furthermore, we propose a novel Kalman-filter embedded communication protocol that can more efficiently use the raw keys generated by QKD.
Cyber-security has become vital for modern networked control systems (NCS). In this paper, we propose that the emerging technology of quantum key distribution (QKD) can be applied to enhance the privacy and security of NCS up to an unbreakable level. QKD can continuously distribute random secret keys with much higher privacy between communication parties, and thus enable the one-time pad encryption that cannot be truly applied in classical networks. We show that the resulting overall security of NCS can be essentially improved, and present a composable definition of security based on the analysis of the key generation and management processes. Moreover, because the security is mainly determined by quantum keys rather than the complexity of encryption algorithms, the control performance can be improved as well by reducing the time delay using simpler algorithms. These advantages are demonstrated by the example of a remotely controlled servo system, showing that the introduction of QKD to NCS can simultaneously improve the security and performance by using the simplest encryption algorithm XOR. Furthermore, we propose a novel Kalman-filter embedded communication protocol that can more efficiently use the raw keys generated by QKD.
The cyber-security of multi-agent control systems has become vital in practice. To protect the communication process between the individual agents over TCP/IP networks, one must encrypt the messages to be sent, which is costly in a large-scale network when high-level security is demanded. To lessen the burden of heavy encryption and decryption processes, we introduce the Homomorphic Encryption to reduce the number of encryption/decryption terminals that are supposed to equip with every agent. The security is enhanced by the quantum key distribution technology, which can generate secret keys that are theoretically absolutely secure even against quantum computation. We proposed a hybrid method that make good use of the randomness of quantum keys, one-time pad and symmetric encryption to make sure the overall security of homomorphic encryption algorithms. Numerical simulations are provided to illustrate how our scheme.
Encrypted control has been extensively studied to ensure the confidentiality of system states and control inputs for networked control systems. This paper presents a computationally efficient encrypted control framework for networked systems enabled by quantum communication. A quantum channel between sensors and actuators is used to generate identical secret keys, whose security is further enhanced through quantum key distribution. These keys enable lightweight encryption and decryption while preserving confidentiality and control accuracy. We develop a novel encryption-decryption architecture for state-feedback control of linear systems based on quantum keys, and characterize the impact of quantum state errors on closed-loop stability. In particular, we establish the existence of a critical threshold on intrinsic quantum noise below which stability is guaranteed. In contrast to classical encrypted control schemes, which may collapse under a single key-bit error, the proposed quantum encrypted control exhibits strong robustness to key imperfections. We further adopt quantization techniques to address the scenarios with limited communication bits in practical situations, and implement privacy protection for quantum keys based on a stochastic quantizer. These results demonstrate that integrating quantum technologies into control systems in a nontrivial and principled manner, even at their current level of maturity, can yield substantial performance gains in reducing computational complexity and improving resilience to key errors while ensuring security against multiple eavesdropping sources.
Cyber-physical systems (CPS) are a technological marvel forming our modern world's backbone. These systems, which integrate physical processes, embedded systems, networking infrastructure, IoT, communication protocols, intelligent algorithms, and other application-specific resources, mark the convergence of computing with control and communication. They unify physical and cyber systems, paving the way for the next generation of critical systems such as autonomous transportation, smart grids, industrial IoT, and more. The next-generation CPS, characterized by their integration of physical processes, embedded systems, networking infrastructure, IoT, communication protocols, and intelligent algorithms, are set to revolutionize our world. These systems will incorporate AI and ML-based algorithms for decision-making and optimization. At the same time, edge and fog computing models will be integrated into the infrastructure to reduce data transmission latencies. New-generation networks like 5G and above will provide high-speed connectivity and seamless integration of devices and components. Digital twins will become a standard tool for simulating new scenarios, predictive maintenance, and more. As security threats for cyber-physical systems evolve alarmingly, robust protection becomes increasingly crucial. Quantum Key Distribution (QKD) is a promising solution in this context. With their ability to provide secure cryptographic key exchanges in the operating environments of cyber-physical systems, QKD protocols are gaining traction as the industry shifts towards quantum computing.
This study proposes a lightweight industrial control protocol based on quantum key distribution (QKD) to enhance security and optimize performance in resource-constrained industrial control systems (ICS). Unlike traditional QKD schemes, primarily optimized for long-distance communication in ideal IT environments, this work introduces a resource-aware QKD architecture tailored explicitly for short-range industrial control networks with constrained computing/storage/bandwidth. The protocol constructs a multi-layered stack—integrating the physical layer, quantum key management layer, data link layer, network layer, and application layer—to enable secure quantum key generation, efficient distribution, and dynamic utilization, while avoiding excessive resource overhead on embedded ICS devices. Furthermore, three key optimization strategies are introduced: (1) resource optimization adopts AES-128 with FPGA acceleration, reducing encryption overhead from 15% to 20% CPU utilization to 3%–5% (validated in Sec. V A); (2) real-time assurance implements deficit-round-robin frame scheduling, guaranteeing <2.5 ms latency for safety-critical commands; and (3) stability enhancement utilizes dual-QKD-link redundancy with 5–8 s failover, improving MTBF from 3000 to 10 000+ h. The security real-time trade-off is quantified via coefficient B = Slevel/(Ddelay × δ) (detailed in Sec. V B), where Slevel ∈ [1,10] represents encryption strength, Ddelay is measured latency, and δ is CPU load. Experimental results show that the balance coefficient B improves from 2.1 ± 0.4 (Modbus) to 5.2 ± 0.6, confirming superior balance. This work provides a feasible technical pathway for securing critical infrastructure in the quantum era. Experiments demonstrate a 75% reduction in computational overhead and a real-time-security balance coefficient of 4.5–6.0, which is higher than that of Modbus and PROFINET.
Quantum secure communication technology, grounded in the principles of quantum mechanics, has revolutionized traditional cryptographic methods, which predominantly rely on mathematical algorithms and logical transformations. Quantum key distribution (QKD) facilitates the secure sharing of symmetric keys between legitimate parties, ensuring the integrity and confidentiality of information in communication channels. Among various QKD schemes, continuous variable quantum key distribution (CV-QKD) has emerged as a viable alternative to the more established discrete variable quantum key distribution (DV-QKD). CV-QKD boasts several advantages, including straightforward deployment, reduced operational costs, and stable signal quality, positioning it as a significant component of the quantum communication landscape. Quantum noise stream cipher (QNSC) represents a technique that employs redundant data streams to encrypt plaintext. Notably, QNSC shares structural similarities with the optical path used in quantum key distribution, allowing for compatibility with existing QKD infrastructure. Furthermore, the keys generated through quantum key distribution ensure absolute security, enabling them to substitute the data streams produced by pseudo-random sequences traditionally used in classical encryption schemes. This substitution enhances the overall security framework of the quantum noise stream encryption approach. The quantum access network (QAN) extends quantum key distribution capabilities from point-to-point connections to point-to-multipoint configurations, thereby becoming an essential component of contemporary network architectures. By interlinking multiple end users with a network backbone, quantum access networks can seamlessly integrate with quantum key distribution protocols. This integration offers a cost-effective and scalable solution for user access to the network. Extensive experimental verifications have demonstrated the viability of downstream access networks, indicating that the merging of quantum access network structures with quantum stream encryption technologies can yield a comprehensive quantum experimental platform. On this platform, security keys are derived through quantum key distribution, which subsequently facilitates the encryption of plaintext information. Notably, experimental validations involving eight users have been successfully executed on this platform, underscoring its practical applicability and effectiveness.
Quantum key distribution (QKD), a cryptographic method grounded in the laws of quantum mechanics rather than computational hardness, promises provably secure communications. Its integration into critical infrastructure offers a pathway to secure resilient operation of next-generation control systems, from power-intensive data centers to remotely operated microreactors located in energy-deprived remote communities. While QKD has been demonstrated in laboratory and network settings, its use in safety-critical control systems remains unexplored where requirements on latency, key availability, and operational stability pose unique challenges. Here, we introduce a QKD-secured data acquisition and control framework for embedding quantum cybersecurity directly into safety-critical cyber-physical systems and report the first end-to-end experimental demonstration in a nuclear reactor. The framework establishes the conditions necessary to achieve secure, low-latency, real-time operation in safety-critical environments. Using a phase-encoding decoy-state BB84 system deployed on Purdue's 10 kWth fully digital research reactor (PUR-1) we validate the model and achieve real-time encryption and decryption of 2,000 reactor signals. Experiments demonstrated a stable secret-key rate of 320 kbps with a quantum bit error rate of 3.8% at 54 km, and maximum optical-fiber distances of 82 km with One-Time Pad (OTP) encryption and 140 km with AES-256. We further evaluated compliance with latency and key availability conditions using three cryptographic schemes (OTP, AES-256, ASCON), finding that all variants supported real-time operation at typical data reporting rates. Our results establish a universal framework for quantum-cybersecurity in safety-critical systems, demonstrating that quantum communication technologies can enable secure, low-latency, real-time operation of nuclear reactors and other critical infrastructure.