# EAIA: An Efficient and Anonymous Identity-Authentication Scheme in 5G-V2V
## 2 Related Work  
In this section, we systematically compare and analyze related research on inter-vehicle mutual authentication. Despite the critical importance of mutual authentication for securing vehicle communication, research focused on inter-vehicle mutual authentication in the absence of infrastructure remains limited. Existing studies primarily concentrate on infrastructure-supported authentication mechanisms, which, while providing certain solutions, still exhibit significant weaknesses in terms of security or efficiency. Firstly, many studies rely on infrastructure support to achieve inter-vehicle mutual authentication. These studies often use Public Key Infrastructure (PKI) or other centralized authentication mechanisms, involving trusted third parties or RSUs for distributing and verifying authentication information. For example, some research proposes methods for distributing digital certificates and keys through RSUs to provide authentication services when vehicles enter a specific area [10]. In this paper, a robust authentication scheme is proposed, using decentralized authentication through vehicle-to-roadside unit communication to continuously update the vehicle sensor network (VSN) information. Only trusted vehicles communicate via a V2V secret communication channel established with RSU assistance [11]. In this scheme, onboard units (OBUs) generate anonymous identities and temporary encryption keys to initiate authentication sessions. Secondly, the legitimacy of vehicles' real and anonymous identities can be verified by a TA. When a vehicle wishes to establish a secure session with another vehicle, it first requests authentication from nearby RSUs. After preliminary processing, the RSU forwards the request through a wired channel to higher-level authorities for identity and reputation verification. Finally, with RSU assistance, session keys are negotiated [12]. A lightweight anonymous batch-verification protocol for V2I and V2V authentication based on elliptic curve cryptography (ECC) has been proposed using Physical Unclonable Functions (PUFs) and biometric keys to prevent RSU capture attacks and OBU intrusions. The design incorporates a feature-embedding strategy with dynamic pseudonyms to restore malicious vehicle identities via a TA. Vehicles within the same RSU domain can authenticate each other and establish session keys, allowing communication in any RSU domain or traffic infrastructure-free environment without repeating authentication. The authors in [13] proposed an efficient privacy-preserving mutual authentication protocol for secure V2V communication in VANETs, setting up law executors (LEs) assumed to be trustworthy and acting as mobile authentication servers. Initially, ordinary vehicles authenticate solely through LEs. If successfully authenticated, the vehicle becomes trusted. Untrusted OBUs can be authenticated by LEs in the regular authentication phase or by trusted OBUs in the trust extension phase. Trusted vehicles can then communicate securely in the secure communication phase. When the key's lifecycle expires, the vehicle's status becomes untrusted, and key revocation is enforced. The authors in [14] designed a lightweight mutual authentication protocol for vehicular networks using cryptographic operations, proposing the concept of vehicle servers (VSs) to provide updated real-time information to requesting vehicles. When a vehicle wishes to communicate with another (e.g., send a warning message), it encrypts the message using its key. The receiving vehicle forwards the requesting vehicle's identity to the VS, which verifies the legitimacy of both vehicles and, if successful, sends the requesting vehicle's key to the other vehicle via a secure channel for decryption and communication. The solution in [15] proposed a hybrid D2D message authentication (HDMA) scheme for 5G-supported VANETs using a novel group signature-based algorithm for V2V mutual authentication. Vehicles entering an RSBS coverage area and seeking services send pseudonyms for initial V2I authentication.