Abstract As the cornerstone of future information security, quantum key distribution (QKD) is evolving towards large-scale hybrid discrete-variable/continuous-variable (DV/CV) multi-domain quantum networks. Meanwhile, multicast-oriented multi-party key negotiation is attracting increasing attention in quantum networks. However, the efficient key provision for multicast services over hybrid DV/CV multi-domain quantum networks remains challenging, due to the limited probability of service success and the inefficient utilization of key resources. Targeting these challenges, this study proposes two key-resource-aware multicast-oriented key provision strategies, namely the link distance-resource balanced key provision strategy and the maximum shared link key provision strategy. The proposed strategies are applicable to hybrid DV/CV multi-domain quantum networks, which are typically implemented by GG02-based intra-domain connections and BB84-based inter-domain connections. Furthermore, the multicast-oriented key provision model is formulated, based on which two heuristic algorithms are designed, i.e., the shared link distance-resource (SLDR) dependent and the maximum shared link distance-resource (MSLDR) dependent multicast-oriented key provision algorithms. Simulation results verify the applicability of the designed algorithms across different multi-domain quantum networks, and demonstrate their superiority over the benchmark algorithms in terms of the success probability of multicast service requests, the number of shared links, and the key resource utilization.
Abstract As the cornerstone of future information security, quantum key distribution (QKD) is evolving towards large-scale hybrid discrete-variable/continuous-variable (DV/CV) multi-domain quantum networks. Meanwhile, multicast-oriented multi-party key negotiation is attracting increasing attention in quantum networks. However, the efficient key provision for multicast services over hybrid DV/CV multi-domain quantum networks remains challenging, due to the limited probability of service success and the inefficient utilization of key resources. Targeting these challenges, this study proposes two key-resource-aware multicast-oriented key provision strategies, namely the link distance-resource balanced key provision strategy and the maximum shared link key provision strategy. The proposed strategies are applicable to hybrid DV/CV multi-domain quantum networks, which are typically implemented by GG02-based intra-domain connections and BB84-based inter-domain connections. Furthermore, the multicast-oriented key provision model is formulated, based on which two heuristic algorithms are designed, i.e., the shared link distance-resource (SLDR) dependent and the maximum shared link distance-resource (MSLDR) dependent multicast-oriented key provision algorithms. Simulation results verify the applicability of the designed algorithms across different multi-domain quantum networks, and demonstrate their superiority over the benchmark algorithms in terms of the success probability of multicast service requests, the number of shared links, and the key resource utilization.
Quantum key distribution (QKD), as one of the pivotal technologies for future-proof security, is progressing toward large-scale networking. Since different QKD protocols have their own potential advantages and shortcomings, the interconnection of metropolitan quantum networks based on heterogeneous protocols is an important step to realize a wide-area quantum network. In this scenario, the provision of inter-domain key services still faces challenges in terms of success probability, security level, and the balance between key supply and demand. Targeting these challenges, this work proposes four secret key rate (SKR) adaptive inter-domain key service provisioning policies based on the dynamic node bypass and elastic SKR slicing, namely, IrB-IaB (inter-domain bypass and intra-domain bypass), IrS-IaS (inter-domain slicing and intra-domain slicing), IrB-IaS (inter-domain bypass and intra-domain slicing), and IrS-IaB (inter-domain slicing and intra-domain bypass). The proposed policies are applicable to multi-domain quantum networks with heterogeneous protocols such as GG02-based metropolitan and BB84-based inter-domain connections, as well as BB84-based metropolitan and TF-based inter-domain connections. Furthermore, the inter-domain key service provisioning model is formulated, and four corresponding SKR-adaptive inter-domain key service provisioning algorithms are designed. Simulation results show that the IrS-IaS algorithm performs better in terms of success probability as well as the equilibrium degree between key supply and demand. The security level is quantitatively evaluated through the number of trusted relays. The IrB-IaB algorithm achieves the lowest number of trusted relays, which is more than 20% lower than the benchmark algorithm, resulting in a higher security level and lower cost. The key resource utilization efficiency is assessed via the equilibrium degree. Both the IrB-IaS and IrS-IaB algorithms have the potential to balance the effectiveness and reliability of quantum networks. In particular, the IrS-IaB algorithm is beneficial in achieving the best trade-off between key resource utilization efficiency and security level.
Most of the existing metropolitan quantum networks are implemented based on a single quantum key distribution protocol, and interconnecting metropolitan quantum networks implemented by different protocols are the development trend of large-scale quantum networks, but there are still some problems in the provision of inter-domain key services, such as low possibility of success and mismatch between key supply and demand. To solve the above problems, this paper proposes two on-demand inter-domain key service provisioning strategies for multi-domain cross-protocol quantum networks, namely, on-demand provisioning strategy based on BB84 bypass first (BB84-BF) and on-demand provisioning strategy based on MDI bypass first (MDI-BF). Meanwhile, a service provisioning model for multi-domain cross-protocol quantum networks is constructed, and an on-demand inter-domain key service provisioning algorithm is designed. Moreover, numerical simulations and performance evaluation are carried out under two scenarios: high key rate demand and low key rate demand for two-domain and three-domain quantum network topologies. Simulation results verify that the proposed on-demand provisioning strategies have better applicability to different multi-domain quantum networks. In addition, for different key rate requirements, the MDI-BF strategy and BB84-BF strategys have different performance advantages under different performance indicators. For example, in terms of the success possibility of inter-domain key service requests, the MDI-BF strategy is more suitable for the low key rate requirements (~30% higher than the traditional strategies in two domain topologies), while the BB84-BF strategy is more suitable for the high key rate requirements (~19% higher than the traditional strategies under two domain topologies). In addition, compared with the traditional strategies, the proposed on-demand provisioning strategies can increase the balance degree between key supply and demand by more than one order of magnitude. Hence, the proposed strategies can reduce the cost of inter-domain key service provisioning and improve the realistic security level.
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.
Quantum key distribution (QKD) can provide long-term security for numerous users. Currently, quantum networks are still in the early stages of small-scale deployment, most of which can only support a single QKD protocol (QKDP). However, with the advancement of various QKDPs, a single-protocol quantum network is no longer sufficient to meet the demands of multiple users, prompting the emergence of multi-protocol quantum networks. Nevertheless, the transition from a single-protocol to a multi-protocol quantum network still faces many challenging issues, such as key negotiation interruptions due to device initialization and channel calibration during protocol updating. To address the quantum key negotiation interruption problem, we propose a seamless key negotiation oriented multi-protocol updating algorithm in this work, which can fulfill the protocol updating requests of different users in quantum metropolitan networks. Furthermore, to better improve network performance while meeting diverse user demands, we propose four heuristic algorithms for optimal QKDP recommendation, focusing on their applications for multi-protocol updating in different types of typical networks. We perform the simulations with different QKDP recommendation algorithms to analyze the impact of the cache time of the key cache area on the key negotiation interruption probability and the time resource utilization. Simulation results demonstrate that the proposed algorithm can reduce the key negotiation interruption probability by 77.7% while increasing the time resource utilization by 15.3% compared to no key cache area.
There exist several initiatives worldwide to deploy quantum key distribution (QKD) over existing fibre networks and achieve quantum-safe security at large scales. To understand the overall QKD network performance, it is required to transition from the analysis of individual links, as done so far, to the characterization of the network as a whole. In this work, we undertake this study by embedding QKD protocols on complex networks, which correctly model the existing fiber networks. We focus on networks with trusted nodes and on continuous-variable (CV) schemes, which have much higher key rates than their discrete-variable (DV) counterparts. In the effective CV network, however, many of the unique properties of complex networks, such as small-worldness and the presence of hubs, are lost due to the fast decay of the key rate with physical distance for CV systems. These properties can be restored when considering a hybrid network consisting of both CV and DV protocols, achieving at the same time high average rate and inter-connectivity. Our work opens the path to the study of QKD complex networks in existing infrastructures.
Quantum Key Distribution (QKD) networks enable unconditionally secure key exchange using quantum mechanical principles. However, routing cryptographic keys across multi-hop quantum networks introduces challenges unique to quantum communication. This survey analyzes and classifies 26 routing strategies proposed between 2013 and 2024 for terrestrial, satellite, and hybrid QKD infrastructures. Dynamic, key-aware routing algorithms have been shown to reduce service rejection rates by 25-40% compared to static shortest-path methods by incorporating real-time key pool availability and link error rates. Multi-path strategies improve resilience against trusted-node compromise by distributing keys across disjoint routes, albeit with an increase in key consumption of 30-60%. SDN-based orchestration frameworks emerge as essential enablers of flexible, QoS-aware routing for hybrid networks integrating terrestrial fibers and intermittent satellite links. Critical research directions include reducing dependence on trusted nodes through quantum repeaters or post-quantum cryptography, developing standardized key management interfaces for interoperability, and adopting AI-driven predictive routing for adapting to fluctuating network states. This comprehensive synthesis of routing algorithms, performance trade-offs, and unresolved issues offers practical guidance for engineering secure, adaptable, and large-scale QKD networks capable of meeting real-world deployment demands.