# Blockchain-Based Authentication in Internet of Vehicles: A Survey
## 2 Background
### Internet of Vehicles
Cloud and edge computing capabilities, processing, and analysis of collected data to transform them into useful information through big data analytics tools to provide services to consumers and businesses are as well positive points for the IoV. In addition, IoV has brought the ability to support diverse types of interaction models including Vehicle-to-Vehicle (V2V), Vehicle-to-Roadside-unit (V2R), Vehicle-to-Infrastructure (V2I), Vehicle-to-Pedestrian (V2P), Vehicle-to-Sensor (V2S), and many others as indicated in Figure 1. V2V and V2R indicate the interaction among the vehicles and the interaction between the vehicles and the RSUs, respectively, via wireless protocols such as WAVE. V2I is the communication between vehicles and infrastructure possibly via Wi-Fi, Long Term Evolution (LTE), or 5G. While V2S represents the onboard sensor communication via Ethernet and Wi-Fi, V2P refers to the communication among vehicles and personal devices such as smartphones via Apple's CarPlay, Open Automotive Alliance Android system, or Near Field Communication [58; 59]. Different layered architectures for IoV frameworks have been proposed in the literature, which differ in the number and/or names of layers proposed. These architectures compete to optimize the number of layers and to enhance the distinguishability between the different layers [57; 58; 60; 61; 62; 63]. The most common IoV architecture can be seen in Figure 2 which defines six layers, namely, physical, communication, processing, services, business, and security. The main responsibility of the physical layer is to gather information about vehicles and their surrounding environment such as vehicle's speed, position, travelling direction, on-road vehicular density, weather conditions, and others through the sensing devices, actuators, GPS modules, and access points installed on the vehicles. RSUs and other personal devices may also be used. The collected data are then transferred in a secure way to the processing layer through the communication layer, which employs diverse wireless communication standards and network modules to guarantee interoperability between the different heterogeneous network entities such as WAVE, WiFi, RFID, Bluetooth, 4G/LTE, UW, and satellites. The processing layer represents the storage, processing, and transformation of the data received from the lower layers into useful information to be used for decision making. This includes the adoption of various big data analytics tools and cloud computing platforms. The services layer then takes the information processed and the decisions made by the processing layer and employs them to provide intelligent IoV services and applications to the end users which can contribute to road safety and traffic efficiency. The business layer's responsibilities can include decisions related to economics investment, budget estimation and regulation, pricing, and operations management. Finally, the security layer concerns about secure and reliable data collection and communication among the different nodes to prevent against diverse number of security attacks and threats that can be encountered in IoV environments. Since security is the main theme of this paper, we will discuss more on this in the coming sections. Figure 1: Communication models in IoV.