We experimentally evaluate the SKR generation for unoptimized QKD pairs in switched QKD and compare the performance of the switched-QKD with relayed-QKD networks to reveal they perform better for short distances and at large networks.
We evaluate the performance of two architectures for network-wide quantum key distribution (QKD): Relayed QKD, which relays keys over multi-link QKD paths for non-adjacent nodes, and Switched QKD, which uses optical switches to dynamically connect arbitrary QKD modules to form direct QKD links between them. An advantage of Switched QKD is that it distributes quantum keys end-to-end, whereas Relayed relies on trusted nodes. However, Switched depends on arbitrary matching of QKD modules. We first experimentally evaluate the performance of commercial DV-QKD modules; for each of three vendors we benchmark the performance in standard/matched module pairs and in unmatched pairs to emulate configurations in the Switched QKD network architecture. The analysis reveals that in some cases a notable variation in the generated secret key rate (SKR) between the matched and unmatched pairs is observed. Driven by these experimental findings, we conduct a comprehensive theoretical analysis that evaluates the network wide performance of the two architectures. Our analysis is based on uniform ring networks, where we derive optimal key management configurations and analytical formulas for the achievable consumed SKR. We compare network performance under varying ring sizes, QKD link losses, QKD receivers' sensitivity and performance penalties of unmatched modules. Our findings indicate that Switched QKD performs better in dense rings (short distances, large node counts), while Relayed QKD is more effective in longer distances and large node counts. Moreover, we confirm that unmatched QKD modules penalties significantly impact the efficiency of Switched QKD architecture.
The rise of quantum computers threatens public key security and its essential role in distributing symmetric keys. QKD offers a promising solution by leveraging quantum principles for secure key distribution between two points. To enable network-wide key distribution, two candidate architectures have emerged: Relayed QKD which relays neighboring generated keys along a path, and Switched QKD which uses optical switches to dynamically connect QKD devices and create key generation sessions between nodes. Both architectures require algorithmic solutions for effective key management and distribution. In prior work, we derived for uniform ring topologies optimal configurations and analytical formulas for keys consumption and compared the Switched and Relayed architectures. In this study, we extend that work by introducing scheduling and key management algorithms for arbitrary topologies and use them to compare these two architectures in non-uniform rings. Our findings reinforce previous conclusions: Switched QKD is more effective for dense (large number of nodes and short distances) networks, such as metropolitan rings, while Relayed QKD outperforms in larger rings with longer distances.
The rise of quantum computers threatens public-key cryptography and its foundational role in secure symmetric key distribution. Quantum Key Distribution (QKD) offers a promising alternative, leveraging quantum principles to securely distribute keys between two endpoints. To enable network-wide key distribution, two main architectures have emerged: Relayed QKD, which forwards keys generated between neighbors along a path, and Switched QKD, which uses optical switches to dynamically establish QKD links between nodes for scheduled key generation sessions. Both architectures require algorithmic solutions for efficient key management and distribution. We present optimal configurations and analytical formulas for uniform rings and compare the performance of the two architectures. We also define generic key management algorithms and apply them to compare the two architectures in non-uniform rings. Our findings are consistent across both uniform and non-uniform rings: Switched QKD is more effective in dense networks (i.e., with many nodes and short distances), while Relayed QKD performs better in larger rings with longer inter-node distances.
In QKD (Quantum Key Distribution) network deployments, the inherent quantum characteristics impose distance limitations due to the difficulty in storing quantum information and the lack of intermediate network devices like classical routers or switches. This paper introduces these limitations and examines international efforts to overcome them. While China and Singapore are utilizing satellites to extend QKD transmission range, European countries and Japan are researching hybrid relay methods using post quantum cryptography (PQC) or digital key relay nodes
Quantum Key Distribution (QKD) has emerged as a promising technology for secure the communication because its security is achieved through the physical laws of quantum mechanics, rather than being based on mathematical problems. In most of the earlier implementations, QKD relied on the direct exchange of the secret keys between two users. Once implemented in a practical system outside of a controlled laboratory setting, QKD experiences complications associated with the limited distances, communication losses, and vulnerabilities to eavesdropping in the multi-user network configurations, compromising its ability to be this third-generation secure communication system. In this work, we show how quantum relay nodes can be implemented as points along a QKD network. The relay nodes provide additional advantages such as extending the communication distances, increasing eavesdropping resistance and allowing for more sophisticated configurations. While relying on theoretical models and experimentally motivated studies, this paper discusses advantages of implementing a relay architecture into a QKD network and highlights technical difficulties that need to be addressed prior to widespread implementation.
With the growing complexity of quantum key distribution (QKD) network structures, aforehand topology design is of great significance to support a large-number of nodes over a large-spatial area. However, the exclusivity of quantum channels, the limitation of key generation capabilities, the variety of QKD protocols and the necessity of untrusted-relay selection, make the optimal topology design a very complicated task. In this research, a hybrid QKD network is studied for the first time from the perspective of topology, by analyzing the topological differences of various QKD protocols. In addition, to make full use of hybrid networking, an analytical model for optimal topology calculation is proposed, to reach the goal of best secure communication service by optimizing the deployment of various QKD devices and the selection of untrusted-relays under a given cost limit. Plentiful simulation results show that hybrid networking and untrusted-relay selection can bring great performance advantages, and then the universality and effectiveness of the proposed analytical model are verified.