# EAIA: An Efficient and Anonymous Identity-Authentication Scheme in 5G-V2V
## 4 System Model
### System Model  
As shown in Figure 1, the 3 GPP 5G system primarily consists of the 5G core network (5 GC) and the 5G Radio Access Network (RAN). In the 5G RAN, each vehicle and RSU connect to the network via wireless channels through gNB. The gNB connects to the 5 GC via wired channels. The system architecture of the 5G core network includes multiple functions such as the Access and Mobility Management Function (AMF), Authentication Server Function (AUSF), and Unified Data Management (UDM). During the registration and authentication process, the AMF handles access requests, authentication, registration, mobility management, and handover control for user equipment (UE). It maintains the authentication and key management for vehicles and interacts with the AUSF. The AUSF is responsible for the authentication and authorization of user equipment, ensuring secure network access and functioning as an authentication server. The UDM provides the storage and management of user data, supporting user profiles, authentication data, and subscription data.  
The 5G-supported V2V identity-authentication protocol involves four participants: the OBU, (RSU), gNB, and the 5G core network. Except for the OBU, the other participants are involved only in the registration phase. In the authentication phase, only two OBUs participate.  
On board unit (OBU): In the 5G-V2X (Vehicle-to-Everything) ecosystem, the OBU is a device installed in vehicles responsible for communication with other vehicles and infrastructure. It acts as a vehicle controller with computational capabilities, sending and storing traffic information and exchanging road condition data between vehicles. Eachvehicle has a unique real identity, denoted as RID, pre-installed by the manufacturer, and serves as a unique registration identifier.  
Road side unit (RSU): The RSU is a critical infrastructure component in the 5G-V2X network, serving as a bridge between vehicles and the network infrastructure. Strategically placed along roads, RSUs provide connectivity and facilitate data exchange between vehicles and the network. They support direct V2X communication and can connect to gNB via fiber optic or high-speed Ethernet to relay information across the core network. RSUs enhance road safety and traffic management by enabling low-latency and high-reliability communication. However, RSUs are not entirely trustworthy entities and are susceptible to attacks by malicious adversaries.  
5G base station (gNB): The next-generation NodeB (gNB) is a 5G base station providing Radio Access Network (RAN) connectivity within the 5G-V2X framework. The gNB manages radio resource allocation and communication connections in the cellular network. By communicating with vehicles and RSUs, the gNB offers wide-area coverage and supports high mobility. It is also responsible for connecting to the core network to ensure data transmission and processing.  
5G core network (5 GC): The 5G core network (5 GC) is the backbone of the 5G-V2X ecosystem, coordinating various network functions and managing data flow between the access network and external services. It comprises multiple network functions (NFs), including the Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), and Policy Control Function (PCF), among others. Each entity performs specific network functions to ensure the efficient operation of the 5G network.