## 2 Literature Review
### Smart Mobility
#### 2.2.2 Countermeasures  
To provide safety and information-related applications on the road, the vehicular ad hoc network (Vanet) has recently received considerable attention in the smart transportation domain. Vanet delivers an infrastructure where vehicles moving on the road can use communications to report traffic congestion, accidents, and road surface conditions to other cars. Although Vanet is an excellent cyber-physical system [46], it has several security and privacy problems, particularly location privacy. To be applied, they must enhance the Vanets applications to preserve the identity and location privacy of cars. However, since a hostile vehicle cannot be followed using a complete privacy-preservation strategy in a cyber security scenario, most users would expect a conditional privacy-preservation approach to safeguarding systems. Group signatures may be used to provide conditional privacy preservation. However, the calculation costs are relatively high. Unlikable pseudo-ID techniques may also produce dependent privacy preservation. However, revoking a malicious vehicle would result in a lengthy revocation list. Unfortunately, any proposed method for verified cater evocation does not enable forward unlikability. Forward unlikability is a challenging criterion for Vanet systems. If a car is hacked and turns malevolent, the vehicle's license should be cancelled immediately. However, the vehicle's previous communications and positions (from before it was hacked) should be safeguarded and unlikable. To address these issues, the authors of this research study [47] provide a lightweight conditional privacy-preservation system that leverages basic hash-chain algorithms to allow accurate identity monitoring by a trusted authority and quick local revocation verification on the road. In Vanet systems, the suggested protocol addresses location privacy, conditional privacy preservation, and forward unlikability. In addition, novel security techniques are presented in this study [48] to enable safe certificate revocation, which is regarded as one of the most demanding design challenges in Vanet networks. Each vehicle that receives a message from another vehicle verifies the sender's certificate. The recipient verifies the sender's certificate. When a sender's certificate is invalid, the recipient ignores the message. If the sender lacks credentials, the receiver will report him to the road side unit and review the message. If the information is correct, the road side unit (RSU) will issue a valid certificate. The road side unit will issue an invalid certificate and add the vehicle to the revocation list otherwise. The RSU replaces a misbehaving car's valid certificate with an invalid certificate to indicate it should be avoided. Multiple vehicles report to the road side unit that a car has a valid certificate and is broadcasting incorrect data. This research paper [49] presents a catalogue of potential solutions, each of which, if put into practice, can dramatically cut the risk of cyberattacks on the communication systems of connected cars in a vanet infrastructure. Five degrees of security architectures may be chosen from the defense options that users can apply. However, cyber attackers have a large terrain of assaults and objectives, and the variations between innocuous and damaging are recorded in terms of the number of people killed and the amount of damage done to transportation infrastructure. Cryptography, zero-knowledge between communication vehicles, and authentication methods with or without a trusted third party are all necessary breakthroughs; in reality, they are inadequate [50; 51; 52], especially today, when more and more automated vehicles are being put onto the roads, which need to cohabit with other types of motorized and non-motorized traffic participants efficiently and safely.