Similar to the Internet, Quantum Key Distribution (QKD) networks typically have diverse participants, such as users, operators, and infrastructure builders. In order to achieve loose functional coupling, a multi-layer structure is frequently indispensable. Nevertheless, once the architecture of the QKD network is designed, further expansion and modification prove to be extremely challenging. To address this issue, a QKD network architecture based on virtual Quantum Key Distribution (VQKD) is proposed. In this architecture, all devices at both ends that are capable of providing consistent quantum keys are regarded as a pair of quantum key distribution devices. The bottom layer is real QKD, while all other layers are virtual QKD. All real and virtual QKDs provide quantum keys to the upper layers. This network structure is an iterative one, and theoretically, the number of layers in a quantum key distribution network can be infinitely increased based on actual needs. In this paper, we present a practical application case. This case addresses the actual needs of network operators, network service providers, and those involved in user network construction. We have designed a three-layer quantum secure communication network exchange structure that is suitable for network infrastructure developers, network operators, and those involved in user network construction. Network infrastructure developers, network operators, and users can carry out network construction, network operation, and user network construction at different network layers, realizing a loosely coupled hierarchical design of quantum secure communication networks. This model can dynamically increase or decrease the number of quantum network exchange layers based on actual needs, without affecting the network exchange of quantum secure communication networks, demonstrating strong versatility and adaptability.
Similar to the Internet, Quantum Key Distribution (QKD) networks typically have diverse participants, such as users, operators, and infrastructure builders. In order to achieve loose functional coupling, a multi-layer structure is frequently indispensable. Nevertheless, once the architecture of the QKD network is designed, further expansion and modification prove to be extremely challenging. To address this issue, a QKD network architecture based on virtual Quantum Key Distribution (VQKD) is proposed. In this architecture, all devices at both ends that are capable of providing consistent quantum keys are regarded as a pair of quantum key distribution devices. The bottom layer is real QKD, while all other layers are virtual QKD. All real and virtual QKDs provide quantum keys to the upper layers. This network structure is an iterative one, and theoretically, the number of layers in a quantum key distribution network can be infinitely increased based on actual needs. In this paper, we present a practical application case. This case addresses the actual needs of network operators, network service providers, and those involved in user network construction. We have designed a three-layer quantum secure communication network exchange structure that is suitable for network infrastructure developers, network operators, and those involved in user network construction. Network infrastructure developers, network operators, and users can carry out network construction, network operation, and user network construction at different network layers, realizing a loosely coupled hierarchical design of quantum secure communication networks. This model can dynamically increase or decrease the number of quantum network exchange layers based on actual needs, without affecting the network exchange of quantum secure communication networks, demonstrating strong versatility and adaptability.
Quantum Key Distribution (QKD) networks allow multiple users to generate and share secret quantum keys with unconditional security. Although many schemes of QKD networks have been presented, they are only concentrated on the system realization and physical implementations. For the complete practical quantum network, a succinct theoretic model that systematically describes the working processes from physical schemes to key process protocols, from network topology to key management, and from quantum communication to classical communication is still absent. One would hope that research and experience have shown that there are certain succinct model in the design of communication network. With demonstration of the different QKD links and the four primary types of quantum networks including probability multiplexing, wavelength multiplexing, time multiplexing and quantum multiplexing, we suggest a layer model for QKD networks which will be compatible with different implementations and protocols. We divide it into four main layers by their functional independency while defining each layer's services and responsibilities in detail, orderly named quantum links layer, quantum networks layer, quantum key distribution protocols process layer, and keys management layer. It will be helpful for the systematic design and construction of real QKD networks.
A global Quantum Key Distribution (QKD) network, as the one developed in the European project SECOQC [1] is an infrastructure capable of realizing long-distance secret key establishment with information-theoretic security. Due to the specificity of their physical layer, the structure and the principle of operation of QKD networks will however significantly differ from the solutions adopted for “classical ” networks. The deployment of QKD networks is indeed far from being straightforward: it implies the con-ception of a network architecture connecting multiple users that may possibly be very far away from each other, all of this while QKD links are currently point-to-point only and intrinsically limited in distance. We will describe the logical architecture we have adopted for QKD networks with the SECOQC project. It is based on the original concept of maintaining a dedicated “network of secrets ” in order to distribute and manage the secret key material produced by QKD devices. We will alo present specific issues related to the development of a stack of network protocols adapted to the specific constraints of such infrastructures [2]. We have also considered QKD networks from a topology viewpoint and study analytically how cost minimization arguments impact on the optimal working points of individual QKD links [3]. We show in particular that, in the perspective of QKD networks, individual QKD links should be operated at an optimal working distance that can be significantly shorter than the maximum distance imposed by detector dark counts. We explain why such results motivate the research of new experimental compromise in practical QKD systems, and illustrate that point by considering the example of the recently developped DPSK QKD system [4].
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.
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) has progressed from a theoretical cryptographic concept to an emerging secure communication infrastructure technology. While early work focused on protocol security and physical-layer feasibility, current research increasingly addresses scalable network deployment, hardware acceleration, and integration with classical communication systems. As QKD expands from point-to-point links to metropolitan, backbone, and hybrid satellite–terrestrial networks, new engineering challenges arise in topology design, entropy generation, real-time key distillation, and multi-vendor interoperability. This survey provides an infrastructure-oriented review of QKD networks, examining architectural models, quantum randomness as a root of trust, FPGA and system-on-chip (SoC) based acceleration techniques, and programmable control-plane integration. Key management system architectures and standardized interfaces are analyzed to highlight their roles in enabling scalable, interoperable deployments. The paper also synthesizes major standardization efforts and deployment initiatives shaping carrier-grade QKD infrastructures. Finally, open engineering challenges, including scalability, control-plane integration, certification harmonization, and hybridization with post-quantum cryptography, are identified, positioning QKD as a foundational component of next-generation secure communication systems.
There is a great attention to quantum technologies in the ICT environment. In particular, when dealing with security matters, the most prominent quantum technology is Quantum Key Distribution (QKD). QKD allows the sharing of symmetric keys with information theoretic security (ITS, i.e. independently of the computational power of the attacker) between two remote network nodes. QKD is the only known method to share a key able to reach ITS. During the last two decades, there has been a tremendous technological progress in QKD research, that has led to the availability of QKD network demonstrators.Software Defined Networks (SDN) enables the automation of service provisioning within network operator infrastructures. With the advent of web-scale services and dynamic network requirements, operators can not anymore deploy their services based on manual intervention or using proprietary vendor solutions. Programmability is key in the next-generation network infrastructure and any new technology must be integrated with this paradigm. Let us highlight that this requirement is even more important with virtual environments, where a Virtual Network Function (VNF) can be deployed in any point-of-presence of the operator. The new 5G deployments will enable operators to have edge computing services supporting different capabilities, thus increasing even more the complexity to deliver services without any automation.In spite of the high potential of QKD, this technology has not yet found its path to wide adoption, commercialization and deployment. QKD is a physical technology that requires the existence of a quantum channel, a physical connection able to transmit quantum bits without perturbation, making hard its integration in networks. The aim of this document is to present how QKD can be deployed in next generation infrastructures, based on realistic scenarios. To do so, this paper describes the technological components of the solutions, as well as the use cases that motivate such effort. These use cases are described from a telecommunication provider's point of view, as they are the actors in charge of deploying QKD systems in their networks.