ABSTRACT Quantum key relay over trusted relay nodes is a practical approach to overcoming the distance limitation of quantum key distribution (QKD) protocols in quantum-secured networking. However, the processing delay incurred by the quantum key relay function increases the quantum key response delay (KRD) which serves as a representative quality-of-service (QoS) metric for quantum-secured services. This QoS degradation becomes more pronounced in large-scale quantum-secured networks. To address this issue, we investigate a proactive quantum key relay algorithm that relays and prepares quantum keys for pairs of QKD nodes prior to requests for quantum-secured services. By jointly considering the length of the relay path, the available quantity of quantum keys, and the remaining lifetimes of the quantum keys, the proposed algorithm selects a pair of QKD nodes and performs proactive quantum key relay to establish a quantum key for the selected pair. The proposed algorithm enables more flexible operation by sequentially dividing the proactive quantum key relay algorithm into two parts: one for a relatively short distance pair of QKD nodes and the other for a long-distance pair of QKD nodes. The simulation results demonstrate that, compared with the on-demand quantum key relay algorithm, the proposed algorithm achieves a relative reduction of up to 89.7% in the modeled KRD, accompanied by a corresponding relative decrease of 13.9% in the provisioning ratio of quantum-secured service. Overall, these findings confirm the effectiveness of the proposed proactive quantum key relay algorithm in achieving short-latency quantum-secured networking.
ABSTRACT Quantum key relay over trusted relay nodes is a practical approach to overcoming the distance limitation of quantum key distribution (QKD) protocols in quantum-secured networking. However, the processing delay incurred by the quantum key relay function increases the quantum key response delay (KRD) which serves as a representative quality-of-service (QoS) metric for quantum-secured services. This QoS degradation becomes more pronounced in large-scale quantum-secured networks. To address this issue, we investigate a proactive quantum key relay algorithm that relays and prepares quantum keys for pairs of QKD nodes prior to requests for quantum-secured services. By jointly considering the length of the relay path, the available quantity of quantum keys, and the remaining lifetimes of the quantum keys, the proposed algorithm selects a pair of QKD nodes and performs proactive quantum key relay to establish a quantum key for the selected pair. The proposed algorithm enables more flexible operation by sequentially dividing the proactive quantum key relay algorithm into two parts: one for a relatively short distance pair of QKD nodes and the other for a long-distance pair of QKD nodes. The simulation results demonstrate that, compared with the on-demand quantum key relay algorithm, the proposed algorithm achieves a relative reduction of up to 89.7% in the modeled KRD, accompanied by a corresponding relative decrease of 13.9% in the provisioning ratio of quantum-secured service. Overall, these findings confirm the effectiveness of the proposed proactive quantum key relay algorithm in achieving short-latency quantum-secured networking.
Quantum key distribution (QKD) is a symmetric key exchange mechanism designed to enhance the security of current communication systems. Although QKD provides unconditional security, it also comes with deployment challenges. One challenge is the distance limitation between the transmitter and receiver, which restricts the large-scale adoption of QKD. To overcome this, trusted relays are used as intermediate nodes, allowing QKD to evolve from distance-limited point-to-point connections to unlimited QKD networks (QKDN). With an increasing deployment of QKD and a growing number of applications requesting keys, quality of service (QoS) constraints must be set for efficient key resource management to alleviate the risk of rejecting application requests. In this work, we integrate key delivery delay and maximum requested key size as QoS constraints in a novel key allocation algorithm built on three QKDN layers – quantum, key management and service. Moreover, we design key relaying using quantum key pools and virtual quantum key pools as storage mechanisms. We use static and dynamic weights for relay path computation and evaluate their impact on the proposed key allocation strategies with QoS constraints and find that static weights show a good overall performance for QKDN, while performance with dynamic weights varies based on historical key consumption data.
By overcoming the distance limit in quantum key distribution (QKD) technology, key relaying over trusted nodes is regarded as an essential function for practical quantum-secured networking. The key relay function consumes a series of costly quantum key resources to establish an end-to-end key in QKD networks (QKDNs); thus, an efficient key relay algorithm is required. To investigate this problem, we developed an integer linear programming (ILP) formulation that maximizes a balanced summation between max-min fairness and efficiency in the key relay. Inspired by the ILP model, this study developed a key-count differential-based proactive key relay (DPKR) heuristic algorithm to provide a scalable solution for key relays in QKDNs. The proposed DPKR algorithm iteratively selects a set of nodes by considering the key-count differential between nodes and establishes an end-to-end key by relaying it over the selected nodes. Owing to the proactive key relay model, an effective key relay route in the key management layer in the QKDN can be calculated solely by the key-count status in the key management layer. The proposed DPKR algorithm reduces manifold order-of-magnitude in the algorithm computation time at the cost of an acceptable loss in the average and minimum numbers of keys from those of the ILP optimization model. The computation time evaluation clearly manifests a scalability of the DPKR algorithm in quantum-secured networking.
Quantum secure communication networks based on quantum key distribution (QKD) technology are gradually improving, which can provide remote and networked key services for multiple users. This paper proposes a key distribution solution for latency and resource optimization in trusted relay QKD networks. In this scheme, the key distribution process between trusted relay nodes is presented as a joint optimization problem by considering the constraints of service delay, bandwidth, path resource consumption, quality loss and remaining quantum key quantity. In this paper, we treat key distribution as a bi-objective minimization problem, maintaining a trade-off between service delay and path resource consumption. Specifically, we propose a dynamic key distribution framework based on linear programming and particle swarm optimization. Simulation results show that the key distribution path selection in this scheme can be adjusted according to the service delay, key quality, and path resource consumption. Compared with the Random and customized OSPF policies, this scheme has higher performance. More specifically, the solution reduced average service latency by 27% while reducing path resource consumption by 560%.
In recent years, noticeable progress has been made in the development of quantum equipment, reflected through the number of successful demonstrations of Quantum Key Distribution (QKD) technology. Although they showcase the great achievements of QKD, many practical difficulties still need to be resolved. Inspired by the significant similarity between mobile ad-hoc networks and QKD technology, we propose a novel quality of service (QoS) model including new metrics for determining the states of public and quantum channels as well as a comprehensive metric of the QKD link. We also propose a novel routing protocol to achieve high-level scalability and minimize consumption of cryptographic keys. Given the limited mobility of nodes in QKD networks, our routing protocol uses the geographical distance and calculated link states to determine the optimal route. It also benefits from a caching mechanism and detection of returning loops to provide effective forwarding while minimizing key consumption and achieving the desired utilization of network links. Simulation results are presented to demonstrate the validity and accuracy of the proposed solutions.
As an emerging technology, Quantum Key Distribution (QKD) can provide information-theoretically secure keys for cryptographic purposes and it attracts worldwide attention. To extend its service capabilities from point-to-point communication to arbitrary remote communication parties, large-scale QKD network construction is underway. However, the dynamic and limited available resources of QKD networks remain a major obstacle to routing design. Numerous studies aim at designing routing schemes to maximize the overall network performance. While these routing schemes efficiently support end-to-end key relaying, their effectiveness diminishes when addressing diverse Quality of Service (QoS) requirements. In this paper, we propose an on-demand routing scheme with QoS provisioning to enhance end-to-end key relaying rates. Our scheme operates in two phases: an on-demand resource probing phase to dynamically update global network resource information and a routing decision phase that leverages a maximum flow model to optimize key relaying while satisfying rate-demand constraints. Simulation results on the SimQN platform demonstrate that the proposed scheme significantly improves end-to-end key relaying through-put and delay, providing effective QoS support for rate-demand QKD applications.
This study proposes a group key service node placement method for quantum key distribution (QKD) networks based on partially trusted relays, aiming to optimize network structure, improve key distribution efficiency, reduce communication delay, and ensure transmission integrity and confidentiality. Based on graph theory, a key information model for the quantum key distribution network is established, which defines node types, functions, and connectivity. Leveraging the secure transmission protocol of quantum keys, the unconditional security of the key during transmission is ensured. Furthermore, this study proposes a QKD network architecture incorporating partially trusted relays, which combines trusted and untrusted relay technologies. An improved p-median model is introduced and solved using a greedy algorithm to ensure secure quantum key distribution and optimal deployment of group key service nodes. Experimental results demonstrate that the location of group key service nodes in quantum key distribution network ensures the minimum number of key service nodes and minimizes the path length from network demand nodes to group key service nodes. Furthermore, this method significantly improves the key distribution efficiency, success rate, security, energy consumption, resource consumption, network coverage, and blind area of quantum key distribution network.