# Blockchain-Based Authentication in Internet of Vehicles: A Survey
## 2 Background  
### Internet of Vehicles  
IoV is an emerging field that mainly incorporates ITS and IoT technologies, while covering a wide range of other technologies and applications such as vehicular information services, advanced wireless communication technologies, cloud computing, edge computing, and automotive electronics to provide intelligent transportation services and enhance the quality of roads. It integrates the intelligent in-vehicle sensor devices with the intra-vehicle and inter-vehicle wireless communication technologies along with Internet technology to collect and exchange vehicle-related and traffic-related data that can be later used for making better road-related actions and decisions. IoV consists of three basic components: (1) the intra-vehicular network, (2) inter-vehicular network, and (3) vehicular mobile Internet [56]. This includes the communication between vehicles in the same vehicular network, the communication between different vehicular networks, and the connection between vehicles and mobiles, respectively. The functionality of IoV imposes equipping vehicles with several smart units and devices including electronic control units, On Board Units (OBUs), sensors, event data records, cameras, GPS modules as well as a diverse number of wired (Controller Area Network and Local Interconnect Network buses) and wireless (i.e., Bluetooth) communication technologies. The former technology to IoV is the VANETS which was basically introduced to improve the traffic efficiency and road safety by establishing connectivity and exchanging information between the moving vehicles with and without the aid of any pre-established roadside infrastructure via different communication modes namely, Wireless Access in Vehicular Environments (WAVE) based Wi-Fi, ad-hoc, and hybrid. Despite its efficiency in addressing road safety and traffic management issues with low operational cost, VANETs exhibit some commercialization problems which include but are not limited to the following [57]:  
1. VANETs' framework could not fully support the global and sustainable services targeted by ITS applications. This is caused by the pure ad-hoc communication architecture, in which an on-road vehicle can lose its granted services once it disconnects from an ad-hoc network. This is due to the inability of collaborating with other alternative reachable networks. 2. Internet connectivity in VANETS could not be ensured, which affects the availability of commercial applications for vehicles' drivers and passengers since those applications rely on reliable Internet connectivity. 3. Despite the rapid technological advancement of personal mobile devices, they could not communicate with VANETs due to the incompatible network architecture. 4. Intelligent decision making, and big data analytics applications were not possible in certain VANETs architectures. This could be related to the computing and storage constraints and the lack of cloud computing services. 5. The application services could not guarantee high level of accuracy, since VANETs localize the computation and processing of traffic data information. The above limitations of VANETs have drawn the attention of researchers and industrial developers to extend the capabilities of the existing vehicular networks to move further steps towards providing more efficient vehicular services and achieving the global objectives of ITS. Consequently, IoV has emerged as an advanced vehicular technology that attempts to overcome the shortcomings of conventional VANETs through supporting a high range of mobility, strong connectivity among vehicles and with roadside infrastructure, reliable Internet connection, and high interactivity with personal devices. IoV can also provide an immediate management of risk situations through maintaining low delay and delivering high reliability and robustness.