Security threats to V2X systems include physical harm, financial incentives, and non-monetary incentives. Attack variants include active and passive attacks and can be performed offline or online. Examples of active attacks include false code/data injection, denial of service (DoS), and alteration of transmitted data. Passive attacks threaten user privacy by linking V2X messages and vehicle movements to individuals. Classifications of V2X attacks include DoS, Sybil, and false data injection. DoS attacks can occur at different network layers, such as physical-layer jamming and network-layer routing-based DoS. Sybil attacks involve creating multiple fake identities to disrupt communications and gain unauthorized access to sensitive information. Spoofing attacks involve an attacker introducing spoofed data into a network in order to disrupt or mislead other nodes. These types of attacks can reduce message delivery efficiency by up to 90%.[G3]

Use of CA

Fig.G1: Use of CA [G4]

The exchange of sensitive information between vehicles and other road users, as well as infrastructure, requires a high level of security to protect against unauthorized access and attacks. V2X security includes several different components such as secure communication protocols, secure data storage, and secure data transmission. One of the key challenges in V2X security is to ensure that vehicle-to-vehicle communications are secure and cannot be intercepted or manipulated by unauthorized parties. This is particularly important for safety-critical applications such as forward collision warning, lane departure warning and electric emergency braking. Other security challenges include protecting against denial-of-service attacks, ensuring message authenticity, and ensuring the privacy of vehicle and road user data. To address these challenges, V2X security systems typically use a combination of encryption, authentication, and secure key management to protect communications and data transmission. In addition, regular security updates and testing are essential to ensure that V2X systems remain secure over time. Overall, ensuring the safety of V2X systems is key to the successful implementation of this technology and the realization of its potential benefits for road safety and efficiency.

Many solutions have been proposed to secure VANETs to address various security issues. One solution is to use a Vehicle Public Key Infrastructure (VPKI) (Figure 1), where each node sends a security message, signs it with its private key, and attaches it to a Certificate Authority (CA). The receiving party of the message obtains the sender's public key and verifies the signature, but this solution requires the CA's public key to be known. Another solution is to use a group signature, but this can cause a lot of overhead. Another solution is a new message checking protocol in which the receiver checks the validity of the sender's certificate and informs the RSU if the sender does not have a valid certificate. Solutions have also been designed for various attacks, such as DOF and Sybil. Switching between different channels or communication technologies can be used to avoid DOF. To protect against Sybil, road radar can be used to compare what was seen with what was heard to isolate malicious vehicles. Also proposed is a reply protocol in which the receiver informs the nearest RSU to check the correctness of the message, and a solution to protect against message suppression attacks by appending time to packets to ensure they are out of sequence. [G4]