## 3 Network Model  
### Quantum Key Distribution Luminescence Network Architecture Based on Hybrid Trusted Relay  
In quantum key distribution networks, the use of relay nodes is a promising solution for achieving remote key distribution. This includes quantum relays, trusted relays, and untrusted relays. The principle of quantum relays is to use quantum entanglement to generate entangled states between two distant nodes, thereby establishing secure long-distance communication [27]. However, quantum relay technology is still immature and costly at present. Therefore, the current approach is to use trusted relay nodes for hop-by-hop communication to generate quantum keys between adjacent nodes, such that large-scale QKDNs are mainly composed of end-users and trusted nodes. However, as the complexity of applications and the number of nodes increase, the security and reliability of the network also face challenges [28]. Finally, researchers introduce untrusted relay nodes as a solution. By using the MDI-QKD protocol, which has device independence and high transmission efficiency, the overall performance of QKDNs can be significantly improved. Thus, we propose a hybrid trust relay-based QKDN scheme (HQKDN), and combine it with the Software Define Network (SDN) framework to achieve the separation of network control and data forwarding operations for flexible network resource management [29]. As shown in Figure 1, the specific architecture of the hybrid Quantum Key Distribution (QKD) network based on Software-Defined Networking (SDN) is presented, and the functional modules at each layer are described in detail below. Data Layer: The data layer is primarily responsible for data transmission and forwarding in optical networks. It achieves high-speed data transmission in optical fibers by scheduling and controlling the transmission paths of optical signals. It also performs the packetization and forwarding of data according to network traffic requirements. QKD Link Layer: The QKD layer is the core layer responsible for implementing quantum key distribution technology. It is responsible for generating, transmitting, and receiving quantum keys while ensuring their security and integrity. In this layer, the BB84 protocol and MDI-QKD protocol are applied for the generation and distribution of quantum keys. Key Management Layer: The key management layer is responsible for managing and distributing the generated quantum keys. It encompasses functions such as key storage, updating, verification, and distribution. In SDN-based optical networks, the key management layer needs to closely collaborate with the network control layer to ensure the secure management and effective utilization of the keys. Control Layer: The control layer serves as the core of SDN-based optical networks, responsible for network control and management. It programs and configures the entire network through a centralized controller, enabling the comprehensive management of the data layer, QKD layer, and key management layer. In the context of QKD technol  
Figure 1: The architecture diagram of a five-layer hybrid trusted relay QKDN based on SDN. ogy, the control layer coordinates and controls the process of quantum key distribution while engaging in information exchange with other layers to ensure network security and performance. Application Layer: The application layer serves as the primary service entity in a QKD network, acting as a bridge between the QKD network and real users. Within this layer, application programs initiate key requests, which are then submitted to the controller. Upon receiving a key request, the application program enters a blocking and waiting phase. Only when the application program receives a response message from the controller can it proceed to the subsequent phase of key generation. The application layer is responsible for defining and implementing high-level protocols and applications required for secure communication.