Quantum key distribution (QKD) has become a promising option for transmitting sensitive data due to the increased maturity of QKD devices and the threat scalable quantum computers imposes on asymmetric public-key cryptosystems. By utilizing existing infrastructure, e.g., amplifier huts and dark fibers, the cost and complexity of deploying QKD networks (QKDNs) can be reduced. In this study, we develop a topology optimization algorithm that minimizes the cost of the QKDN deployment and maximizes the key capacity between any pair of nodes. We present three deployment upgrade strategies for facilitating the encryption of increasing throughput of QKD-secured optical transport networks and enabling a pay-as-you-grow approach. Comparing different strategies in a capacity-planning study allows operators to assess the scalability of deployments and upgrades. Depending on the availability requirements, our results compare the cost of protection measures. We confirm that adding trusted nodes is the most cost-efficient upgrading strategy based on our analysis.
Quantum key distribution (QKD) has become a promising option for transmitting sensitive data due to the increased maturity of QKD devices and the threat scalable quantum computers imposes on asymmetric public-key cryptosystems. By utilizing existing infrastructure, e.g., amplifier huts and dark fibers, the cost and complexity of deploying QKD networks (QKDNs) can be reduced. In this study, we develop a topology optimization algorithm that minimizes the cost of the QKDN deployment and maximizes the key capacity between any pair of nodes. We present three deployment upgrade strategies for facilitating the encryption of increasing throughput of QKD-secured optical transport networks and enabling a pay-as-you-grow approach. Comparing different strategies in a capacity-planning study allows operators to assess the scalability of deployments and upgrades. Depending on the availability requirements, our results compare the cost of protection measures. We confirm that adding trusted nodes is the most cost-efficient upgrading strategy based on our analysis.
The technological maturity of Quantum Key Distribution (QKD) products have generated high demand for secure key distribution in transmitting sensitive data. To provide this service, long-haul network operators are exploring strategies for network-wide deployment of QKD devices while utilizing existing infrastructure. One approach is to place trusted nodes at existing in-line amplifier huts in the network. In this study, we present a near-optimal fiber span aggregation algorithm, which effectively minimizes the number of trusted nodes between Points-of-Presences (PoPs) in the network. In this study, we evaluate six different topological QKD network deployments and eight different technological QKD network deployments in terms of the total secure key rate, as well as the number of QKD fiber pairs deployed. Our results indicate that the span aggregation algorithm increases the distance between each trusted node by up to 20%, thereby reducing the overall number of trusted nodes. Capacity planning for various topologies and technology deployments on simulated Secure Application Entity (SAE) requests is undertaken. Our proposed capacity planning shows that a baseline deployment with span aggregation using a QKD device with a cut-off distance of 140 km can save up to 3 times the number of QKD deployed fibers as compared to a minimum spanning tree-based low-cost deployment.
The maturity and developments of quantum key distribution (QKD) enable its application for encrypting dense wavelength-division multiplexing networks (DWDMNs), ensuring security in the presence of scalable quantum computers. The potential infrastructure reuse and costly deployment of a QKD network (QKDN) require jointly optimized deployment and utilization. We develop and solve a multi-layer problem formulation that fulfills the required keys of the DWDMN demands with the cost-minimized QKDN and maximized reuse of the present infrastructure. Our approach proves the feasibility of currently available QKD devices to encrypt nation-wide DWDMN with multi-period network planning. Furthermore, we compare static and dynamic routing approaches to quantify the advantage of software-defined networking for key management networks (KMNs). Depending on the network load, our multi-layer optimization shows potential savings between 9% and 45% of QKD devices compared to the baseline. Additionally optimizing the operation with dynamic routing increases the performance further, but the gain is negligible for encrypting DWDMNs.
Quantum key distribution (QKD) uses the laws of quantum mechanics to distribute secret keys with information-theoretic security. To realize QKD for secure communications among multiple distant users, fiber-based QKD networks can be deployed with today's available technologies. Incorporating QKD into existing wavelength-division multiplexing (WDM) network infrastructure provides a practical way to reduce the difficulty and cost of QKD networking. Nonetheless, the costs of QKD nodes and QKD links are still considered as the major barriers to long-distance QKD network deployment in practice. In this work, we study how to minimize the cost of deploying QKD-over-WDM backbone networks. We introduce a general architecture of QKD-over-WDM backbone networks. A novel cost-oriented model is defined to elaborate the cost-minimized problem, in which various QKD network components including QKD transceivers, QKD auxiliary equipment for QKD backbone nodes and trusted repeater nodes (TRNs), and QKD links are considered. The physical-layer parameters such as secret-key rate, physical distance, and the layout of TRNs are also incorporated in our defined model. We develop an integer linear programming (ILP) model and a novel cost-efficient QKD networking (CEQN) heuristic algorithm to address the cost-minimized problem. The extensive simulations indicate that our proposed approaches are effective in reducing the cost of deploying QKD-over-WDM backbone networks, where the designed CEQN algorithm is efficient to demonstrate similar to the ILP model. Finally, some open issues in future work are discussed, given that this work only presents an early highlevel analysis as opposed to a definitive detailed model.
Quantum key distribution (QKD) is a promising technology that can provide future-proof security. With the emergence of multiple advanced QKD protocols, the QKD protocol upgrading for a metropolitan quantum optical network (MQON) is critical for fulfilling the requirements of users for secret keys with a high security level. Conventionally, due to the lack of effective QKD protocol upgrading strategies for MQONs, massive amounts of resources have to be consumed during QKD protocol upgrading, resulting in high costs. In order to reduce the costs for practical implementation of QKD protocol upgrading, in this work, a new policy of QKD protocol upgrading is proposed, where the bypass technique is adopted to decouple multiple protocols from the linking patterns for efficient resource utilization. Moreover, we illustrate a multi-role QKD node structure for enabling the harmonious operation of multiple QKD protocols. A mixed integer linear programming (MILP) model and a novel divided-packet-based QKD protocol upgrading algorithm are designed to save costs by relying on flexible traffic management. We also propose a fixed-chain-based QKD protocol upgrading algorithm with fixed traffic management for achieving low costs. Simulation results indicate that the proposed heuristic algorithms are significantly more cost effective than the associated benchmark algorithms, while the MILP model can reduce the cost of protocol upgrading by 41% compared with the benchmark.
Quantum key distribution (QKD) offers unconditional information security by allowing two distant users to establish a common encryption key resilient to hacking. Resultingly, QKD networks interconnecting critical infrastructure and enabling the secure exchange of classified information, can provide a solution to the increasing number of successful cyberattacks. To efficiently deploy quantum networks, the technology must be integrated over existing communication infrastructure, such as optical fibre links. Yet, QKD poses stringent requirements on the conditions of the network over which it is deployed. This work demonstrates the first quantum communication network in Cyprus via the deployment of a multi-node quantum network, exploiting existing commercial underground optical fibre. The network employs bidirectional occupation of fibres and wavelength multiplexing in a ring architecture to achieve, with minimal use of dark fibres, high-rate QKD. Results obtained reveal consistent key generation rates across all nodes, confirming reliable operation in a real-world environment. This deployment highlights the feasibility of leveraging existing telecom infrastructure for quantum-secured communication, marking a significant step toward scalable and cost-effective quantum networks suited for critical applications.
Quantum Key Distribution (QKD) has demonstrated unique and significant advantages in secure communication. In particular, Measurement-Device-Independent QKD (MDI-QKD), which is independent of measurement devices, increases data transmission distances and addresses the issue of low security in trusted relays. Therefore, in this work, we investigate QKD networks based on trusted and untrusted relays over optical backbone networks, providing a cost-optimal solution for the deployment and implementation of QKD networks. Specifically, this paper describes the QKD network and defines a new cost model, which not only fully considers the diverse impact factors of deployment costs but also meets the requirements for sharing network elements in response to different QKD chain requests. Based on cost model, this paper further proposes a cost-optimal heuristic algorithm for hybrid QKD network deployment, which can provide an economical and secure deployment solution for QKD networks. Extensive simulation experiments are conducted and the experimental results show that the proposed method outperforms current mainstream QKD network deployment algorithms in both deployment cost and security. Moreover, as the network scale increases, the advantages of our algorithm become more pronounced. Compared to mainstream algorithms, our method achieve an improvement of 17.7% -64.3% in cost savings and 1.19 to 3.24 times in security levels.