## 2 Related Work  
[PERSON] et al. [17] discussed the various security challenges in V2X communication, including authenticity, confidentiality, integrity, availability, and privacy. It emphasizes the need for secure key management, secure message exchange, and secure vehicle authentication to mitigate these challenges. [PERSON] et al. [18] discussed the security challenges and opportunities of 5G-enabled V2X communication. They emphasize the need for secure and reliable communication, including confidentiality, integrity, and authenticity, to ensure user privacy and safety. Therefore, this section further investigates various secure key management approaches and their weaknesses. Key management is a crucial aspect of any cryptographic security scheme. It encompasses creating, distributing, updating, and removing cryptography keys [19]. Secure communication is established by exchanging keys through an insecure channel or using pre-existing keys. Asymmetric encryption techniques necessitate the sharing of a public key, which is done through a trusted third-party entity known as a Certificate Authority (CA) that is recognized by all parties involved in the data communication. Symmetric encryption algorithms utilize a shared secret key for encryption and decryption [20]. This feature makes symmetric encryption algorithms faster than asymmetric encryption algorithms. However, the drawback is that it can be challenging to establish the symmetric key without a secure channel in V2X networks. In addition, the parties need to develop a framework of trust relationships to authenticate the ownership of the keys before starting a secure communication. The public key infrastructure (PKI)-based scheme [21; 22; 23] is commonly used in V2X networks to validate the ownership of keys [24]. However, these PKI-based systems require a trusted authority (TA) to store the certificates for all registered vehicles. Nevertheless, if the anonymity of vehicles is needed, the vehicle will have more than one certificate. This increases the number of certificate TA must store, which increases storage overheads, and makes it difficult to search for a certificate in a sizeable V2X network. Trust frameworks are classified as a centralized trusted third-party or fully distributed trust. However, due to dynamic and temporary relationships between vehicles, the centralized approach is not practical or secure in networks like V2X networks. This has been discussed in detail in [25; 26]. Therefore, recent research has tried to find distributed trust solutions. Integrity and authenticity of the key is achieved using digital signature and hash functions. In a centralized system, a public key can be signed by a certificate authority trusted by both parties. Then, the receiving party can validate the public key sent via an unsecure communication channel. In distributed systems, threshold cryptography-based algorithms can be used. [PERSON] and [PERSON] [27] proposed a bilinear pairing scheme that assumes the key generator is trusted. However, using a unique device ID can make it challenging to update keys and requires a secure channel for private key transfer. Self-certified public keys [28] combine PKI with the identity-based public key, which is generated by using the unique node id and a random number. Then, the node broadcasts its witness values so others can use witness values and unique id to calculate the public key. However, this approach is not scalable, requiring a reliable broadcasting protocol and large storage to store witnesses. Certificateless public key schemes are variants of ID-based schemes [29; 30], which allow networks to initialize with threshold-based secret sharing schemes so that the master private key is agreed upon among the nodes. A new node can join the network by contacting a threshold number of nodes. Nodes can calculate public keys by using publicly available information, hence avoiding the requirement of the certificate authority.