# The Security Perspectives of Vehicular Networks: A Taxonomical Analysis of Attacks and Solutions
## 2 Preliminary Understanding of VANETs
### Architecture of VANETs  
The architecture of VANET can be described based on the components [6]. A generic VANET architecture is illustrated in Figure 2. It demonstrates various components and parties involved in a VANET and also shows communication techniques. VANETs are made up of many components like vehicles (electric and nonelectric), on-board units of vehicles, roadside units, and pedestrians, communication channels like Dedicated Short Range Communication (DSRC), cellular networks, and charging grids of electric vehicles [7; 8; 9]. Two types of communication can be observed in VANETs: Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I), and reversely, Infrastructure-to-Vehicle (I2V). Infrastructure-to-Infrastructure (I2I) communication takes place among roadside units and also with base stations. They use the internet as a backbone. To distribute the credentials or keys, trusted authorities also use this communication type. The components of the architecture are shown in Figure 3.  
Figure 2: General architecture of VANET. _Mobile component_: All vehicles like cars, jeeps, trucks, buses, motorcycles, and pedestrians fall in this category. It also includes all those components or devices which are carried by passengers and those components which remain in the vehicle. Examples of these components and devices are on-board units, Personal Digital Assistant (PDA), navigation devices such as Global Positioning System (GPS), laptops, and smart mobile phones, etc. _Application Unit_: It is the front end of the driver module. It is an application that is either provided by the manufacturer of the On-Board Unit (OBU), or it may be obtained from an external source. For example, in the case of PDA, applications may be downloaded from various resources using cloud applications. _Onboard Unit_: An Onboard Unit (OBU) is a device that is placed in the vehicle used for communication with other vehicles using various communication technologies. It can also communicate with infrastructural components or Road-Side Units (RSUs) such as traffic lights, charging spots of electric vehicles, and trusted authority. For this, it may use some other mechanism of communication like 3G, LTE, VoLTE, or 4G networks. OBU further consists of multiple components like sensors, storage, GPS, a processor, and an interface for communication. Other components that may be used here are a Tamper-Proof Device (TPD) [10], event data recorder (EDR) [11], and GPS receiver [12]. OBUs are designed to consume less power so that the vehicles' functions can be executed smoothly. _Infrastructural components_: These components don't move, but play important role in network communication. Some components are placed on the roads and are called the Road-Side Units (RSUs). For example, charging spots, poles, and traffic lights are considered as RSUs. _Road-Side Unit (RSU)_: These units are configured with antennas, processors, sensors, charging spots, and storage systems. They are generally placed alongside the road, but in many cases, these are also placed in parking areas and sometimes at other locations feasible for communication coverage. _Trusted Authority (TA)_: To implement security in VANETs, there is always a need for a trusted authority which handles the security issues. A trusted authority (TA) is a centralized or decentralized authority responsible for various activities like registration of vehicle users, OBUs, and RSUs [13; 14]. These authorities are located in such a place where all the traffic is easily manageable. TAs have systems with high computational power, large storage capacity, and consume large amounts of power without any interruption. All these systems form the central infrastructure of the VANETs. These TAs can observe data traffic flowing in between various vehicles and can identify any suspicious activity. Various types of attacks may also be identified and stopped by taking appropriate action like removing a malicious node or stopping traffic from that malicious node.