## 1 Introduction  
The vehicle ad hoc network (VANET) is an innovative field that can improve driving safety, traffic efficiency, and safety management by information transmission between cars and public infrastructure through different communication mechanisms, such as vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication. Systems such as IEEE 802.11p were designed to meet the requirements of ITS architectures in order to achieve the above. Although different aspects of VANETs are being examined, there is much interest in initiating the deployment of this system. Cars are linked together in vehicle networks through ad hoc formation to form a wireless network called ad hoc vehicle networks. Typical VANETs are composed of roadside units (RSUs), onboard units (OBUs), proxy servers, and servers for administration and computers, vehicles, registry authorities, and location-based applications. There is a traffic center made up of both private and public sector firms, and every roadside unit (also known as roadside infrastructure) is connected to the transport center. The VANET network model is based on a two-level network model where the trusted authority (TA) is set as the first level and the RSUs and vehicles are set as the second level. It could be described as follows:  
* **Trusted Authority**--TA is strongly trusted by all network parties and has appropriate computing, networking, and storage capabilities. It also registers RSUs and vehicles, generating initial security parameters for all vehicles and RSUs after a successful connection. * **Roadside Unit**--RSUs reflect the deployment of stationary infrastructure on the road, intersections, and bus stops, serving the interface between TA and vehicles--authenticating vehicle traffic messages and forwarding them to the center of authority. * **Vehicle**--each car unit is fitted with an onboard unit (OBU) that enables the vehicle to interact with other cars and stationary units. A vehicular ad hoc network is created by applying the principles of a mobile ad hoc network (MANET)--spontaneous creation of a wireless network of mobile devices in the field of vehicles. In such networks, cars can exchange information with each other and with stationary receivers. VANET can use any type of wireless technology; however, the most commonly used is WLAN. There are many potential benefits of a VANET network (Figure 1). It can, for example:  
* take action to initiate braking when the car ahead is beginning to brake,
* use platooning (a method for driving a group of vehicles together),
* provide ongoing information about traffic congestion, and
* accelerate the call to public services in the event of accidents. The problems of such a network include the ability to manage multiple vehicles at the same time and defend against external attacks; in the event of overload, errors, or breaking into the system, a life-threatening situation for users arises. The initial development process of any VANET network should deal with security issues. In this paper, we focus on Sybil and bogus attacks, among different security issues. [PERSON] [1] first introduced the Sybil attack in the context of peer-to-peer networks. In a Sybil attack, the attacker creates a large number of false identities with which he can propagate the messages to other network participants. It poses a serious security risk as the  
Figure 1: The idea of VANET network functioning. attacker can send false messages and simulate his location (the attacker may claim to be in multiple places at once) [2]. Due to the increased number of vehicles, it is possible to carry out a DDoS attack by overloading other neighboring units. Moreover, in voting-based systems, an attacker can easily outvote the real participants, leading to a decision in his favor. The Sybil attack presents a significant threat to VANET as a successful vehicle could claim to have witnessed an accident or a traffic jam, which would alter the proposed route for any other vehicle.