Quantum key distribution (QKD) is an essential branch of quantum communications that facilitates future-proof security. In the near future, large-scale quantum networks will inevitably encounter diverse QKD protocols, ultimately resulting in a multi-protocol quantum network. Motivated by the evolution of advanced QKD protocols, this article introduces a pivotal enabler for multi-protocol quantum networks: software-defined heterogeneous QKD chaining (HQKDC). In contrast to the conventional QKD chain using a single protocol and a single connectivity pattern, a heterogeneous QKD chain is established relying on multiple protocols and diverse connectivity patterns. We elaborate the HQKDC framework by describing the structures of various QKD chains and proposing an architecture of software-defined HQKDC over optical networks. The software defined networking paradigm and optical networks can facilitate the orchestration and deployment of heterogeneous QKD chains, respectively. Furthermore, we present and evaluate the strategies for heterogeneous QKD chain deployment, as well as devise and demonstrate the workflow for heterogeneous QKD chain orchestration. Finally, we discuss open issues toward the practical QKD network and quantum Internet.
Quantum key distribution (QKD) is an essential branch of quantum communications that facilitates future-proof security. In the near future, large-scale quantum networks will inevitably encounter diverse QKD protocols, ultimately resulting in a multi-protocol quantum network. Motivated by the evolution of advanced QKD protocols, this article introduces a pivotal enabler for multi-protocol quantum networks: software-defined heterogeneous QKD chaining (HQKDC). In contrast to the conventional QKD chain using a single protocol and a single connectivity pattern, a heterogeneous QKD chain is established relying on multiple protocols and diverse connectivity patterns. We elaborate the HQKDC framework by describing the structures of various QKD chains and proposing an architecture of software-defined HQKDC over optical networks. The software defined networking paradigm and optical networks can facilitate the orchestration and deployment of heterogeneous QKD chains, respectively. Furthermore, we present and evaluate the strategies for heterogeneous QKD chain deployment, as well as devise and demonstrate the workflow for heterogeneous QKD chain orchestration. Finally, we discuss open issues toward the practical QKD network and quantum Internet.
The global Internet appears to users as a unified, seamless infrastructure, but in reality, it is composed of multiple interconnected networks: separate domains with different management and policies. This unified behavior is made possible by complexity-hiding mechanisms and inter-domain coordination protocols, which are critical components of modern networking. As we approach a paradigm shift driven by quantum technologies, new challenges and opportunities emerge. Quantum information processing enables capabilities that classical systems cannot achieve, including the potential to compromise public key infrastructures that support today’s network security. Quantum key distribution (QKD) offers a promising avenue by implementing a key agreement protocol that is information-theoretically secure against computational attack. However, to fully leverage QKD, networks must be adapted to the unique constraints of quantum communication, integrating both quantum bit transmission and secure key distribution across multiple domains. This paper discusses the interconnection of quantum key distribution networks (QKDNs) and presents a distributed, standards-aligned orchestration mechanism designed to manage QKD networks spanning multiple administrative domains. Our solution builds on existing QKDN standards to facilitate interoperability and practical deployment in heterogeneous environments and has been validated on a heterogeneous multi-domain network comprising three interconnected autonomous domains.
Abstract As the first stage of the quantum Internet, quantum key distribution (QKD) networks hold the promise of providing long-term security for diverse users. Most existing QKD networks have been constructed based on independent QKD protocols, and they commonly rely on the deployment of single-protocol trusted relay chains for long reach. Driven by the evolution of QKD protocols, large-scale QKD networking is expected to migrate from a single-protocol to a multi-protocol paradigm, during which some useful evolutionary elements for the later stages of the quantum Internet may be incorporated. In this work, we delve into a pivotal technique for large-scale QKD networking, namely, multi-protocol relay chaining. A multi-protocol relay chain is established by connecting a set of trusted/untrusted relays relying on multiple QKD protocols between a pair of QKD nodes. The structures of diverse multi-protocol relay chains are described, based on which the associated model is formulated and the policies are defined for the deployment of multi-protocol relay chains. Furthermore, we propose three multi-protocol relay chaining heuristics. Numerical simulations indicate that the designed heuristics can effectively reduce the number of trusted relays deployed and enhance the average security level versus the commonly used single-protocol trusted relay chaining methods on backbone network topologies.
Up to now, Quantum Key Distribution (QKD) Network architectures were confined to relatively small networks. Some theoretical and standardization work was carried out at the framework level but its real-world application is still to be proven. Here, we present a novel architecture for QKD Networks, which is based on the SDN approach, and the components needed to scale to large networks. A well-defined functionality of a minimal set of universal modules allows to define the flow of information among them, and this specifies their interfaces and the architecture. We show that this scheme allows to reuse many already proposed interface definitions requiring just minor adaptation and facilitating the real-world deployment. A QKD Network testbed demonstration following these principles is mentioned. We further elaborate on interfaces needed to scale to very large networks, enabling orchestrations of different types or network monitoring tools. The latter have not been considered in depth up to now, but are needed to support automation and advanced capabilities, multidomain networks, slicing, heterogeneity, resource discovery, etc., which will be necessary to scale to large networks. The dynamicity of the quantum level in this scheme allows a significant reduction of the need of QKD devices on the metropolitan scale, an increased robustness of the service, improving its quality and overall network management, showing that the presented architecture is highly appropriate for telecom operators.
Quantum Key Distribution (QKD) is one of the major cryptographic solutions to tackle the security threats associated to future computational advances, in particular those coming from quantum computing. At the most simple level, QKD can be seen as a highly secure source of symmetric secret keys in two separated places. Nonetheless, the lack of standardization and the strong requirements from the physical layer makes this technology very difficult to integrate in existing infrastructure.However, the success of QKD networks radically depends on the degree in which they can be adopted in the existing infrastructure, and it is a must that it happens via standard protocols and interfaces. The flexibility of novel network paradigms, like Software-Defined Networking (SDN), allows for a faster adoption of new concepts, hardware and services in telecommunications networks. This paradigm can be used for quantum communications, allowing for a fast and scalable deployment of quantum technologies and services in the telecommunications network to a degree that was simply impossible in previous schemes, where the different network devices and their connections should be modified, one by one, to create a quantum communications channel.This tutorial provides an introduction to existing QKD technologies and networks, followed by a descriptive explanation on how SDN principles can be utilized to abstract and integrate QKD systems as part of the network management. This will help to reduce the time-to-market for quantum technologies, and also will make quantum cryptography available as a service to be capitalized by the network operators.
The existence of quantum computing presents an existential threat to the traditional cryptographic algorithms, and there is a need to create communication mechanisms that are fundamentally secure. In this regard, the concept of Quantum Key Distribution (QKD) provides information-theoretic security, which is founded on quantum mechanics. Nevertheless, conventional QKD protocols have serious shortcomings such as lack of distance in communication, vulnerability to side-channel attacks, and inability to support the large-scale heterogeneous network. We suggest that HQNet-QKD a Hybrid Quantum Key Distribution framework can help solve these issues by offering a more secure, scalable and future-proof key exchange framework in hybrid classical-quantum networks. To support multi-layered security, the proposed architecture is a network ensuring the smoothness of decoy-state BB84, Measurement-Device-Independent QKD (MDI-QKD), entanglement/twin-field-based QKD with verifiable Secret Sharing (VSS) and Post-Quantum Cryptography (PQC). It provides a complete methodology such as system architecture, mathematical modeling, and end-to-end key synthesis. When used over a distance of 300 km, simulation and testing have shown that HQNet-QKD can achieve up to2.7×higher secret key rate (SKR) than conventional methods, secret communication at 700 km and resilience to both quantum and classical attacks more than 96%. In addition, the framework guarantees forward secrecy, detector-side immunity, contextbound key derivation, and composability and thus resistant to current and future adversaries. It has a low-computational overhead modular design, making it trivial to deploy in a real world, in applications like quantum-secured 5G backbones, cloud data centers, critical infrastructure, and satellite-based communication systems. The findings make HQNet-QKD a new generation solution to quantum-safe secure communication and the first step towards the implementation of the quantum internet.