# Blockchain-Based Authentication in Internet of Vehicles: A Survey
## 3 Security Issues in IoV and VANETs
### Security Threats and Attacks in Vehicular Networks  
As stated previously, different types of security attacks can be launched against IoV or VANETs, whether passive or active, insider or outsider. However, the common factor of all of them is that they constitute a serious threat to the security of the users, the integrity of the flown data, and consequently the safety of the vehicles' drivers and passengers. Various security attacks and threats in vehicular networks (i.e., IoV and VANETs) have been defined in the literature [89; 95; 98; 99]. Following is some of the most common ones:  
* Channel Interference Attack: This is also known as jamming attack, which is the act of interfering with the wireless communication links to hinder and disrupt the quality of communication between connected IoV devices. * Denial of Service (DoS) Attack: In this attack the attacker floods the IoV network with fake unnecessary requests so that the service provider is no longer able to handle the legitimate requests issued by the genuine users. * Distributed Denial of Service (DDoS) Attack: It is an advanced type of DoS attack, in which the fake requests are launched from several distributed nodes forming botnets. * Man-in-the-Middle Attack: In this attack, an attacker places itself in the middle of two communicating legitimate entities to receive the data from the sender and then forward it to the receiver. When the message passes through the attacker, he/she could modify it before forwarding it to the receiver or just reveal its content. * Message Tampering Attack: This attack aims to corrupt the messages and spread false information in the network by manipulating and fabricating the contents of the communicated messages. This can badly affect the road safety and the services provided by IoV thereby harming passengers and drivers. * Eavesdropping Attack: It is also referred to as traffic analysis attack, in which the attacker monitors the network to track vehicle routes for some malicious purposes. The attacker eavesdrops on the communication channels to examine the messages flowing in the network. * Malware Attack: In this attack, the attacker injects malicious software or viruses in the system files to contaminate the network, which can be leveraged to disrupt the network services and/or to manipulate users' data. * Message Holding Attack: Here, the attacker drops some sensitive messages that hold important data about road conditions that could greatly affect the decision of the drivers on road and thus the road safety is compromised. It also enables the drivers to keep these messages for future use (replaying) in the network. The above-defined attacks are examples of common security threats that can affect the confidentiality and integrity of IoV data, as well as the availability of the entire IoV system. Table 2 depicts a mapping between the various presented security attacks and the security requirements affected by each of them. However, since our target in this survey paper is to review and discuss the authentication-related issues in IoV, we dedicate more focus to the attacks and threats that target the authentication domain specifically. Therefore, Table 3 illustrates the authentication attacks with their targeted OSI layer along with some proposed solutions, and following are their definitions:  
* Sybil Attack: An adversary creates multiple fictitious vehicles on the road from a single node/vehicle by allocating it different identities to appear as it represents separate entities. In other words, an attacker creates (and then controls) more than one identity on a single physical node. This implies that other entities in the network will not be able to judge if the data originate from a single vehicle or multiple vehicles. This attack can be used to affect the route selection of a target vehicle by creating a fake traffic jam on the road which forces the targeted victim vehicle to choose an alternative path.