# Security Challenges of Location Privacy in VANETs and State-of-the-Art Solutions: A Survey
## 3 Related Work
### Other Schemes  
Reference [71], presented a new baseline metric for the analysis of mixing effects at possible mixing zone locations. The optimum mixing zone structure can be studied using mixture optimization techniques. They describe a mixing zone as a region of a specified form and scale that can be defined anywhere. The mixing influence of the mixing zone is calculated prior to the extension of the mixing zone using flow-based metrics. These schemes mostly do not ensure full privacy in situations where changing pseudonyms inside a low-traffic environment. However, the scheme depends on fixed mixed zones that are planted on road-side changing pseudonyms in mixed zones make it more difficult for an adversary to learn anything about their identity. Reference [72] proposed modifying the nickname to social sites, which are simply public areas, such as where the traffic light turns red or at the corner of a parking lot or a shopping center. Two basic pseudonym shift approaches are suggested in these articles. Both cars stuck at the signalized intersection in front of the red light, change the username when the traffic light turns orange. The parking area outside the shopping center will change its name shortly before entering the parking lot. By this technique, better location privacy can be achieved when vehicles changed their pseudonym near highly social spots. can also assist vehicles to change their pseudonym at the right place and right movement. Reference [73] suggested a pseudonym reform policy focused on a road-side network, named the Vehicle Position Privacy Zone (VLPZ). The VLPZ concept is close to the current road-side facilities, such as petrol stations, charging points for electric cars and toll booths. The simple VLPZ is made up of two pieces. (i) A single entry point called a router, and (ii) an egress level called an aggregator. Vehicles reach at VLPZ one after the other on one lane. Once the car enters the router, it ceases transmitting protection signals and moves to a VLPZ lane that is arbitrarily and secretly allocated to the router. Vehicles can remain in the VLPZ for a random period. For e.g., if the VLPZ is placed at a gas station, it is time for the driver to fill the fuel tank of the car. Vehicles must change their pseudonym before they leave the VLPZ via the aggregator. However, the order of exit varies from the order of entry, as the time of residency of the car is arbitrary. The key usage of multiple lanes for this tactic is to confuse the opponent. In reality, if the vehicle starts transmitting safety signals before reaching the VLPZ, the enemy does not know the lane of the vehicle or anticipate when the vehicle does exit the VLPZ. Therefore, the First-In-First-out (FIFO) attack cannot be carried out, as the final order and the start order are distinct. In this paper [74], found the path and number of vehicles inside the range to be mixed background parameters. The car senses k neighboring vehicles at a distance less than the minimum distance and updates the username even if it has a specific path within the range of contact. In the simulation, the total distance is assumed to be 4.25 meters. References [75; 76] suggested a Density-based Privacy Location (DPL) approach. It is based on a zone known as a nickname that affects the K intensity level. When a (k-1) neighborhood is located inside the set, the vehicle must adjust its nickname inside the K density field. The method of changing the pseudonym of vehicles continuously or at some stage it is accepted, is a solution in VANETs. Reference [76] introduced changes to [77]. In a mixed context, the author suggested adding rpm, gap between vehicles and road segments. They also recommended that bits (flags) be included in the protected post. A vehicle shall change its nickname if k neighboring vehicles have the same rank as themselves and its flag is equivalent to one. The goal of these changes is to maximize the probability that several automobiles can update their nickname at the same time.