## 1 Introduction
With the growing adoption of blockchain technology across various sectors, including transportation [6], this technology has also shown promise in resolving the challenges within VANETs. Blockchain technology provides a decentralized, secure, and trustworthy database maintained by network nodes [7; 8]. In this way, it can be used to track, organize, and verify interactions among vehicles in the network. In addition, blockchain technology can be also employed for securization purposes. Cybersecurity threats to vehicular ad hoc networks (VANETs) have escalated in recent years, primarily due to their critical role in managing sensitive vehicular data [9]. The conventional centralized systems, typically operated by vehicle service providers, have demonstrated several security shortcomings. These systems often fail to offer the robust defense mechanisms necessary to protect against sophisticated cyberthreats, thus resulting in notable vulnerabilities within vehicular networks [10]. Additionally, the proliferation of wireless connected devices has exponentially increased the complexity of ensuring secure vehicular communications [11]. The intricate web of data exchange within VANETs demands a security solution that transcends the capabilities of traditional centralized systems. Herein lies the potential of blockchaintechnology--it offers a decentralized approach that inherently enhances the security, performance, and scalability of VANETs [12]. Blockchain technology's application in VANETs extends beyond mere communication security [13; 14]. It revolutionizes the entire ecosystem by enabling immutable recordkeeping for vehicular history, thereby ensuring data integrity and fostering a transparent environment for data exchange. This immutable nature of blockchain technology is particularly pivotal, as it ensures that once vehicle data are recorded on the ledger, they cannot be altered or tampered with, thereby instilling trust in the vehicular data records [15]. In most prior approaches, vehicle security in VANETs was accomplished each time it entered the territory of a roadside unit (RSU). Relying solely on a single RSU presents a multitude of challenges. Firstly, it can become a performance bottleneck, especially in high-density areas where numerous vehicles might be entering or exiting simultaneously, thereby leading to latency in certification processes. Secondly, a solitary RSU becomes a single point of failure; if it malfunctions or becomes compromised, it can disrupt the certification of all the vehicles under its jurisdiction. This can also lead to potential security vulnerabilities, where malicious entities might target the RSU to either gain unauthorized access or to disrupt normal operations. Furthermore, there is an inherent lack of redundancy, meaning that if one RSU is down or is facing technical glitches, there is not an immediate backup system in place to continue the vehicle certification. Integrating blockchain technology can alleviate some of these concerns [16; 17]. The decentralized nature of the blockchain ensures that no single point of failure exists, thereby enhancing the robustness and resilience of the system [18]. Every transaction, in this case, vehicle certifications, can be recorded on the blockchain, thus making the data tamper-proof and ensuring its integrity. Moreover, the blockchain's consensus mechanisms can be leveraged to validate vehicle entries, thereby reducing the burden on a single RSU and distributing the task across multiple nodes or participants in the network. This not only streamlines the certification process, but also introduces an added layer of security, thus making it exceedingly difficult for malicious actors to compromise the system. In other words, the transition from traditional centralized systems to blockchain-based solutions equips VANETs with enhanced resilience against data breaches and unauthorized access. The decentralized nature of the blockchain mitigates the risk of single points of failure, which are inherent in centralized systems.