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Journal of Optical Communications and Networking

Comparison and optimization of different routing methods for meshed QKD networks using trusted nodes

Tim Johann, Mario Wenning, Daniel Giemsa, Annika Dochhan, Matthias Gunkel, Tobias Fehenberger, Stephan M. Pachnicke

Published Feb 9, 2024• 19 citations
Publisher

Abstract

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.

DOI
10.1364/jocn.509269

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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 key distribution (QKD) protocols generate a same secret key at two nodes which are at different locations. Such key is used to encrypt and decrypt messages for unconditionally secure communications through a classical channel. Originally, QKD protocols are designed to work between two nodes which are directly connected through a point-to-point quantum channel. Currently, commercial QKD systems have limited range and key rate. To increase key rate and extend range, the key generated by QKD at one end node is relayed hop-by-hop to the other end node through multiple trusted nodes. In a QKD network with multiple pairs of communicating nodes, routing deals with the issue of deciding for each pair, which trusted nodes are used to form a path connecting the end nodes. This paper presents an overview of QKD and highlights the differences between QKD routing as compared to classical routing. The challenges of QKD routing are presented. Existing works dealing with the challenges are surveyed. This paper ends with a discussion on remaining research issues.
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) 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.
Quantum key distribution (QKD) is an encrypted communication technique based on the principles of quantum mechanics that ensures communication security by exploiting the properties of quantum states. Currently, the transmission efficiency of the QKD system is low. Trusted relay technology is used to solve this problem and achieve long-distance transmission. However, trusted relaying alone cannot decrypt the issues of poor link stability and the low utilization of key resources. To further optimize the system performance, we propose a dynamic routing algorithm. One of the improvement schemes includes the following: firstly, an adjustable-size quantum key pool (QKP) is designed, which can dynamically adjust the size of the refreshing pool according to the actual demand. Secondly, the utilization of key resources is improved by using the residual quantum key model to dynamically obtain the remaining key amount in the QKP and set the key amount threshold. We calculate the link-blocking probability and track the blocking intensity and blocking entry by combining the Poisson process, thus realizing the evaluation of the link stability. Finally, the number of remaining keys in the QKP and the link-blocking probability combine with the random wandering model as the basis of the route selection for the QKD dynamic routing algorithm to achieve efficient key path selection. We validated the algorithm by comparing it with other algorithms on the Mininet simulation platform, and the algorithm proved to have a better performance in terms of congestion avoidance, delay reduction, and improved QKD efficiency. This scheme provides a novel and efficient way to solve the problems in existing QKD systems. It effectively improves the transmission efficiency and strengthens the system’s security by dynamically obtaining the critical volume, accurately evaluating the link state, and selecting the optimal critical path.
With the development of quantum computing and computer science, the risk of traditional cryptographic algorithms being cracked is increasing. Therefore, quantum key distribution (QKD) technology based on quantum physical properties has been developed to ensure the security of information communication. Large-scale QKD networks can be built using trusted relay technology, but the hops encryption and decryption process of trusted relay will consume extra keys, which makes it particularly important to choose a reasonable path to reduce the consumption of extra keys during key distribution. The existing routing algorithms mainly focus on the number of remaining keys and hops, but ignore the congestion information of the network, resulting in a high key exchange failure rate and an increase in key consumption. In view of this background, we propose a load balancing routing (LBR) algorithm, which can realize congestion control in QKD network by dynamically detecting link state with SDN controller. Simulation results show that LBR improves key request success rate by more than 10% and key utilization efficiency by about 5% compared with existing methods.
As quantum key distribution becomes increasingly practical, questions of how to effectively employ it in large-scale networks and over large distances becomes increasingly important. To that end, in this work, we model the performance of the E91 entanglement based QKD protocol when operating in a network consisting of both quantum repeaters and trusted nodes. We propose a number of routing protocols for this network and compare their performance under different usage scenarios. Through our modeling, we investigate optimal placement and number of trusted nodes versus repeaters depending on device performance (e.g., quality of the repeater's measurement devices). Along the way we discover interesting lessons determining what are the important physical aspects to improve for upcoming quantum networks in order to improve secure communication rates.