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arXiv:2509.09453 · IEEE Network

Toward Quantum-Safe Scalable Networks: An Open, Standards-Aware Key Management Framework

Ane Sanz, Asier Atutxa, David Franco, Jasone Astorga, Eduardo Jacob, Diego R. Lopez

Published Dec 12, 2025• 2 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1109/mnet.2025.3636584

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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.
With the advent of powerful quantum computers, an emerging quantum-resilient security mechanism within existing networks is crucial. Thus, Quantum Key Distribution (QKD), which generates symmetric secret keys with Information-Theoretical Security (ITS) for secure point-to-point communication, is present as a solution. Despite QKD’s potential, its deployment is challenging due to significant investment and infrastructure requirements. Using state-of-the-art technology, the maximum distance between nodes is limited to hundreds of kilometers, necessitating multiple nodes to relay keys. For now, QKD Network (QKDN) relies on software-defined networking (SDN) and a central orchestrator, but this centralized approach has limitations. Hence, the main challenge is to select an efficient path between key relays to avoid communication failure. To address these challenges, a more distributed approach could be envisioned. In this paper, we propose to leverage one of the distributed routing protocols, OSPF, to redefine and improve the current architecture. We propose a novel QKDN-based OSPF (Open Shortest Path First) architecture for efficient key relay routing, offering a completely different dimension to the overall network management: we modify QKDN architecture to exploit the OSPF networks and present a QKD-enabled OSPF version capable of computing the best path for key relay, offering a cost-effective and scalable solution for widespread QKD adoption.
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) 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.
The advent of quantum computing threatens classical cryptographic mechanisms, demanding new strategies for securing communication networks. Since real-world networks cannot be fully Quantum Key Distribution (QKD)-enabled due to infrastructure constraints, practical security solutions must support hybrid operation. This paper presents an adaptive security framework that enables quantum-safe communications across real-world heterogeneous networks by combining QKD and Post-Quantum Cryptography (PQC). Building upon a hierarchical key management architecture with Virtual Key Management Systems (vKMS) and a centralized Quantum Security Controller (QuSeC), the framework dynamically assigns security levels based on node capabilities. By transitioning between pure QKD, hybrid, and PQC modes, it ensures end-to-end quantum-safe protection regardless of the underlying node capabilities. The framework has been implemented and validated on a Kubernetes-based containerized testbed, demonstrating robust operation and performance across all scenarios. Results highlight its potential to support the gradual integration of quantum-safe technologies into existing infrastructures, paving the way toward fully quantum-safe communication networks.
Abstract Quantum key distribution (QKD) is a means of generating keys between a pair of computing hosts that is theoretically secure against cryptanalysis, even by a quantum computer. Although there is much active research into improving the QKD technology itself, there is still significant work to be done to apply engineering methodology and determine how it can be practically built to scale within an enterprise IT environment. Significant challenges exist in building a practical key management service (KMS) for use in a metropolitan network. QKD is generally a point-to-point technique only and is subject to steep performance constraints. The integration of QKD into enterprise-level computing has been researched, to enable quantum-safe communication. A novel method for constructing a KMS is presented that allows arbitrary computing hosts on one site to establish multiple secure communication sessions with the hosts of another site. A key exchange protocol is proposed where symmetric private keys are granted to hosts while satisfying the scalability needs of an enterprise population of users. The KMS operates within a layered architectural style that is able to interoperate with various underlying QKD implementations. Variable levels of security for the host population are enforced through a policy engine. A network layer provides key generation across a network of nodes connected by quantum links. Scheduling and routing functionality allows quantum key material to be relayed across trusted nodes. Optimizations are performed to match the real-time host demand for key material with the capacity afforded by the infrastructure. The result is a flexible and scalable architecture that is suitable for enterprise use and independent of any specific QKD technology.
Quantum-key-distribution (QKD) networks can theoretically generate quantum secret keys that are completely secure for an entire communication system. The rate of key distribution is low and decreases exponentially with increasing distance. A classic trusted relay (CTR) uses additional keys to enhance security distance in QKD networks. In practice, the assurance of security for certain relay nodes is still lacking, despite the fact that CTR requires that all nodes be trusted. Owing to channel unreliability, system faults accumulate during the key relay, thereby increasing the probability of CTR failing to distribute the secret key. The failure of a successful key relay would then result in the subsequent destruction of all the keys involved in the process, which leads to the wasting of the quantum secret key and reduction system encryption. Accordingly, reducing the impact of CTR failures and realising the key security distribution of remote quantum networks have become new challenges that require the development of a new survivability scheme. In this study, a software-defined networking (SDN) technique is introduced to circumvent this drawback by utilising the flexibility provided by the SDN paradigm for better QKD network management efficiency. In particular, a novel survivability model called software-defined quantum key relay failure (SDQKRF) is proposed in this paper in which a new function is developed and added to the SDN controller. According to the simulation results, SDN over a QKD network using the SDQKRF model is more reliable and performs better in terms of the key generation ratio, key utilisation rate, recovery after failure, avalanche effect, and service blocking rate than a regular QKD network without the SDQTRF model.