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Journal of Optical Communications and Networking

Comparison of distributed and centralized quantum key management systems for meshed QKD networks

Mario Wenning, Jonas Berl, Tobias Fehenberger, Carmen Mas Machuca

Published Jan 10, 2025• 7 citations
Publisher

Abstract

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.

DOI
10.1364/jocn.542054

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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.
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With the advent of quantum computing, the increasing threats to security poses a great challenge to communication networks. Recent innovations in this field resulted in promising technologies such as Quantum Key Distribution (QKD), which enables the generation of unconditionally secure keys, establishing secure communications between remote nodes. Additionally, QKD networks enable the interconnection of multi-node architectures, extending the point-to-point nature of QKD. However, due to the limitations of the current state of technology, the scalability of QKD networks remains a challenge toward feasible implementations. When it comes to long-distance implementations, trusted relay nodes partially solve the distance issue through the forwarding of the distributed keys, allowing applications that do not have a direct QKD link to securely share key material. Even though the relay procedure itself has been extensively studied, the establishment of the relaying node path still lacks a solution. This paper proposes an innovative network architecture that solves the challenges of Key Management System (KMS) identification, relay path discovery, and scalability of QKD networks by integrating Software-Defined Networking (SDN) principles, and establishing high-level virtual KMSs (vKMS) in each node and creating a new entity called the Quantum Security Controller (QuSeC). The vKMS serves the end-user key requests, managing the multiple KMSs within the node and abstracting the user from discovering the correct KMS. Additionally, based on the high-level view of the network topology and status, the QuSeC serves the path discovery requests from vKMSs, computing the end-to-end (E2E) relay path and applying security policies. The paper also provides a security analysis of the proposal, identifying the security levels of the architecture and analyzing the core networking security properties, and a performance evaluation that confirms the feasibility and scalability of the proposal.
Quantum Key Distribution (QKD) takes a short time to process encryption and authentication messages as an advanced security key distribution. Open Shortest Path First (OSPF) routing used on existing QKD networks uses more security keys. Software-Defined Networking (SDN) exists to control the core network, make routes easier to find and reduce the use of security keys. One of the benefits of SDN is that the controller can customize the routing scheme and save the use of secure keys. Based on the topology and scenarios, the link state protocol test results show that using keys increased the number of hops traversed by five to fourteen keys. We can see the five keys constant when testing the distance vector protocol. The average test time difference between the two protocols is about 3.438 seconds for the link state protocol and 2.687 seconds for the distance vector algorithm.
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) is a network security technology that generates encryption keys in real time and randomly during information transmission. This research implements a QKD network based on a software-defined network (SDN) by taking advantage of its advantages, such as saving resources to search for alternative routes and monitoring links to determine whether the conditions in each router network meet the needs or not. Path selection is made using metrics, such as the hop count metric using the routing information protocol (RIP) and the cost using open shortest path first (OSPF). Based on the results of routing performance testing on the QKD network based on SDN, tested ten times to get an average value, OSPF routing is faster at finding alternative routes than RIP routing. The test results for RIP routing throughput of 9.22 ms, delay of 0.76 ms, packet loss of 0.0044%, and convergence time of 10.64 ms. The results for OSPF routing throughput of 9.32 ms, delay of 0.75 ms, packet loss of 0.0039%, and convergence time of 10.51 ms.
This paper aims to address the challenge of designing secure and high-performance quantum key distribution networks (QKDNs), which are essential for encrypted communication in the era of quantum computing. Focusing on the control and management (CM) layer essential for monitoring and routing, the study emphasizes centrally managed software-defined networking (SDN). We begin by analyzing QKDN routing characteristics needed for evaluating two existing architectures and proposed new CM layer implementation. Following the theoretical analysis, we conduct a discrete-event-based simulation in which the proposed architecture is compared to an existing one, which serves as a performance baseline. The results provide recommendations based on use cases for which different architectures show superiority and offer valuable insights into the development and evaluation of CM architectures for QKDNs.