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IEEE International Mediterranean Conference on Communications and Networking (MeditCom)

Relaying Schemes and Rate-distance trade-off for Multihop QKD

David Pérez-Castro, Ana Fernández Vilas, Manuel Fernández‐Veiga, Rebeca P. Dı́az Redondo

Published Jul 8, 2024• 0 citations
Publisher

Abstract

In recent years, quantum communications have garnered considerable attention for their potential to enhance network security. Quantum Key Distribution (QKD) protocols, which promise theoretically secure key generation for remote nodes, have been a primary focus. However, QKD faces significant challenges due to its limited range, especially for fiber-based channels, until quantum repeaters are technologically feasible. Consequently, research efforts have been redirected towards se-cure communication via QKD nodes within multi-hop networks, as a first step towards realizing the quantum internet. In this paper, we propose and analyze a key relay protocol (KRP) for secure quantum key generation within a three-node network, which can be extended to more than two hops in a straightforward manner. We analyzed security under two different sets of assumptions at each node plus accurately evaluated the achievable key rate via numerical methods. Finally, we discuss the advantages and limitations of the proposed protocol.

DOI
10.1109/meditcom61057.2024.10621261

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In recent years, quantum communications have garnered considerable attention for their potential to enhance network security. Quantum Key Distribution (QKD) protocols, which promise theoretically secure key generation for remote nodes, have been a primary focus. However, QKD faces significant challenges due to its limited range, especially for fiber-based channels, until quantum repeaters are technologically feasible. Consequently, research efforts have been redirected towards se-cure communication via QKD nodes within multi-hop networks, as a first step towards realizing the quantum internet. In this paper, we propose and analyze a key relay protocol (KRP) for secure quantum key generation within a three-node network, which can be extended to more than two hops in a straightforward manner. We analyzed security under two different sets of assumptions at each node plus accurately evaluated the achievable key rate via numerical methods. Finally, we discuss the advantages and limitations of the proposed protocol.
In a cyber–physical system, quantum key distribution (QKD) protocols can provide a continuous supply of common secret key bits for secure communications between the control center and a remote device. QKD protocols operate on a peer-to-peer basis between two adjacent nodes and are distance-limited. Hence, trusted nodes are installed between two communicating end nodes for a better QKD range and key rate. These trusted nodes relay in a hop-by-hop manner, key bits generated in the first hop to the other end node. At each trusted node, the first hop key bits are encrypted by other locally generated key bits before being relayed. Since QKD process is stochastic, secret key bits are generated at different rates at different hops. Thus, buffer is needed at a trusted node to temporally hold some key bits while waiting for other key bits. There is no existing work that accounts for such a realistic relaying operation in deriving the key rate. This article contributes to developing a key rate model to determine accurately the end-to-end rates across multiple trusted nodes. We have evaluated accuracy of the proposed model through extensive simulations. The results show that there exist an optimal number of trusted nodes for a given distance between two end nodes. For example, the optimal number of relays increases from four for 100 km to six for 200 km.
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.
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.
Absorption, scattering, and turbulence experienced in underwater channels severely limit the range of quantum communication links. In this paper, as a potential solution to overcome range limitations, we investigate a multi-hop underwater quantum key distribution (QKD) where intermediate nodes between the source and destination nodes help the key distribution. We consider the deployment of passive relays that simply redirect the qubits to the next relay node or the receiver without any measurement. Based on the near-field analysis, we present the performance of a relay-assisted QKD scheme in terms of quantum bit error rate and secret key rate in different water types and turbulence conditions. We further investigate the effect of system parameters such as aperture size and detector field of view on the performance. Our results demonstrate under what conditions relay-assisted QKD can be beneficial and what end-to-end transmission distances can be supported with a multi-hop underwater QKD system.
Quantum key distribution (QKD) allows the distribution of secret keys for quantum-secure communication between two distant parties, vital in the quantum computing era in order to protect against quantum-enabled attackers. However, overcoming rate-distance limits in QKD and the establishment of quantum key distribution networks necessitate key relaying over trusted nodes. This process may be resource-intensive, consuming a substantial share of the scarce QKD key material to establish end-to-end secret keys. Hence, an efficient scheme for key relaying and the establishment of end-to-end key pools is essential for practical and extended quantum-secured networking. In this paper, we propose and compare two protocols for managing, storing, and distributing secret key material in QKD networks, addressing challenges such as the success rate of key requests, key consumption, and overhead resulting from relaying. We present an innovative, fully decentralized key distribution strategy as an alternative to the traditional hop-by-hop relaying via trusted nodes, where three experiments are considered to evaluate performance metrics under varying key demand. Our results show that the decentralized pre-flooding approach achieves higher success rates as application demands increase. This analysis highlights the strengths of each approach in enhancing QKD network performance, offering valuable insights for developing robust key distribution strategies in different scenarios.
The paper addresses the Quantum Networks (QN) performance with Quantum Key Distribution (QKD) protocols.The focus is on networks with multi-hop paths (multiple QKD links with intermediate nodes).QKD emerged as a promising technology to ensure unconditioned communications security by exploiting the Quantum Computing (QC) and quantum principles.While the Point-to-Point (P2P) QKD links are well understood for several QKD protocols, the challenges concern the development of QN with multiple intermediate nodes and links.The deployment of quantum-secure communication systems over very large distances requires multi-hop QN.This paper presents a simulation-based case study for multi-hop QKD networks, focusing on the performance evaluation and the Cyber Security implications.The framework could be used to evaluate end-to-end key generation rates, latency, and resilience under various network topologies and link conditions.This methodology will allow to properly investigate how the network-level security policies can be integrated with QKD protocols to detect and mitigate both passive and active attacks.One could find out the trade-offs between hop count, security margins, and throughput, providing insights into the design of robust and scalable quantumsecure communication infrastructures.This study will support the research about the integration of the QKD with the classical network management, conventional security mechanisms and advanced Cyber defense strategies.