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.
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.
Time-sharing of Quantum Key Distribution (QKD) transceivers with the help of optical switches and a central Software-Defined Networking (SDN) controller is a promising technique to better amortize the large investments required to build a Quantum Key Distribution Network (QKDN). In this work, we investigate the implications of introducing Time-Division Multiplexing (TDM) in trusted-relay QKDNs at the wide-area network scale in terms of performance and cost-saving. To this end, we developed both a Mixed Integer Linear Programming (qTDM-MILP) model and a Heuristic Algorithm (qTDM-HA) to solve the allocation of QKD transceivers and network resources for a novel switched QKDN operating scheme: qTDM-QKDN. Our heuristic method provides a close-to-optimal resource planning for the offline problem that computes the minimum number of QKD transceivers and optical switch ports at each node, as well as the number of quantum channels on each link required to satisfy a target set of end-to-end secret-keyrate demands. Moreover, both the model and the heuristic provide the time fractions that each QKD transceiver needs to peer with each neighbor QKD transceiver. We compared our proposed model and heuristic algorithm for cost minimization with non-time sharing QKD transceivers (nTDM) as baseline. The results show that qTDM can achieve substantial cost-savings in the range of 10%–40% compared to nTDM. Furthermore, this work sheds light on the selection of the value for the working cycle T and its influence on network performance. • TDM optimizes QKD networks, enhancing efficiency and cost-effectiveness. • A MILP model and the qTDM-HA ease resource allocation in large-scale QKD networks. • The tools provide outstanding solutions from 10% to 40% in terms of cost-savings. • TDM minimizes the number of dedicated QKD transceivers by using shared ones wisely.
Time-sharing of Quantum Key Distribution (QKD) transceivers with the help of optical switches and a central Software-Defined Networking (SDN) controller is a promising technique to better amortize the large investments required to build a Quantum Key Distribution Network (QKDN). In this work, we investigate the implications of introducing Time-Division Multiplexing (TDM) in trusted-relay QKDNs at the wide-area network scale in terms of performance and cost-saving. To this end, we developed both a Mixed Integer Linear Programming (qTDM-MILP) model and a Heuristic Algorithm (qTDM-HA) to solve the allocation of QKD transceivers and network resources for a novel switched QKDN operating scheme: qTDM-QKDN. Our heuristic method provides a close-to-optimal resource planning for the offline problem that computes the minimum number of QKD transceivers and optical switch ports at each node, as well as the number of quantum channels on each link required to satisfy a target set of end-to-end secret-keyrate demands. Moreover, both the model and the heuristic provide the time fractions that each QKD transceiver needs to peer with each neighbor QKD transceiver. We compared our proposed model and heuristic algorithm for cost minimization with non-time sharing QKD transceivers (nTDM) as baseline. The results show that qTDM can achieve substantial cost-savings in the range of 10%-40% compared to nTDM. Furthermore, this work sheds light on the selection of the value for the working cycle T and its influence on network performance.
Recent developments in quantum key distribution (QKD) demonstrate the maturity of securing sensitive data against the emerging quantum computing threat. For QKD-secured long-haul and meshed optical transport networks (OTNs), quantum key management systems (QKMSs) are essential to overcome current distance limitations of available QKD devices. In this work, we present and compare two implementations of QKMSs, analyzing their scalability with an emulated QKD network (QKDN) utilizing recorded performance metrics from deployed QKD devices. First, we use a state-of-the-art Internet routing scheme, i.e., open shortest path first (OSPF), demonstrating that key management entities (KMEs) can solve the key routing problem utilizing distributed routing. Second, we apply software-defined networking (SDN) to implement centralized routing with a SDN controller. This paper compares distributed with centralized key routing regarding scalability, throughput, and latency. Both schemes facilitate up to six key relays between any pair of nodes in parallel with average key relay durations per hop below 300 ms given the Nobel-Germany topology and any-to-any demand matrix. With a network-wide joint key routing optimization in the SDN controller, up to 16.7% higher demands can be served compared to distributed key routing. Within the inherent compatibility of our study to network-function virtualization (NFV), we guideline future integration of QKMSs into deployed OTNs.
Quantum key distribution (QKD) appears as a promising technique for encrypted communication, preserving security even in the presence of a future powerful quantum computer. At the same time, communication infrastructure becomes increasingly complex, and the exponentially increasing traffic volume makes the application of QKD a challenging task. In addition, current hardware for QKD modules is still subject to research to gain maturity, to guarantee secret key rates, and to mitigate key rate fluctuations and instabilities. Our study analyzes and optimizes five routing algorithms to efficiently use the secret keys as a resource in meshed national-wide networks. By fulfilling distinct security and performance levels, the algorithms are compared with respect to key performance indicators and optimized for blocking probabilities, load balancing, or the management traffic amount. Depending on the application, our study allows operators to choose a well-suited algorithm and gives performance estimates, including an assessment of the performance gap to globally optimized algorithms.
Quantum-secured networking constitutes a layering architecture comprising a user network and a quantum key distribution network (QKDN). In the wavelength division multiplexing-based quantum-secured optical networking, wavelength and quantum key are scarce resources in the user network and QKDN, respectively; hence, an efficient resource dimensioning algorithm is required for practical quantum-secured services. Therefore, we investigated a resource dimensioning problem for the standardization-compatible quantum-secured networking model, where a data routing path in the user network and a quantum key relay path in the QKDN are interdependent. As benchmarking solutions, we first developed integer linear programming (ILP) formulations for wavelength and quantum key resource optimal quantum-secured networking. To obtain the tractable solution, an iterative heuristic algorithm was proposed, in which a path of a quantum-secured service was calculated by considering the statuses of both wavelength and quantum key resources. Simulation study on practical backbone topologies revealed that the proposed heuristic algorithm reduced manifold order-of-magnitude in the algorithm computation time at the costs of acceptable overheads in the wavelength and quantum key resources, from those of the ILP optimizations.
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.