VANET is an emergent technology with promising future as well as great challenges especially in its security. In this paper, we focus on VANET security frameworks presented in three parts. The first presents an extensive overview of VANET security characteristics and challenges as well as requirements. These requirements should be taken into consideration to enable the implementation of secure VANET infrastructure with efficient communication between parties. We give the details of the recent security architectures and the well-known security standards protocols. The second focuses on a novel classification of the different attacks known in the VANET literature and their related solutions. The third is a comparison between some of these solutions based on well-known security criteria in VANET. Then we draw attention to different open issues and technical challenges related to VANET security, which can help researchers for future use.
VANET aims to insure safe drive by improving the traffic flow and therefore significantly reducing the car accidents. The latter is solved by providing appropriate information to the driver or to the vehicle. Still, any alteration of this real-time information may lead to system failure impacting people safety on the road. To insure its smooth functioning, securing this information becomes a must and hence it is on the top outlook of security researchers.
VANET is a special class of mobile ad-hoc network with predefined routes (roads). It relies on specific authorities for registration and management, Roadside units (RSUs) and On-Board units (OBUs). RSUs are widespread on the road edges to fulfill specific services and OBUs are installed in the vehicles navigating in VANET. All vehicles are moving freely on road network and communicating with each other or with RSUs and specific authorities.
Using DSRC (Dedicated Short Range Communication) in a single or multi-hop, the communication mode is either V2V (Vehicle-toVehicle), V2I (Vehicle-to-Infrastructure) or hybrid.
In the coming years, most of the vehicles in VANET will be equipped with on-board wireless device (OBU), GPS (Global Positioning System), EDR (Event Data Recorder) and sensors (radar and ladar) as shown in Fig. 1. These equipments are used to sense traffic congestions and status. Then automatically take appropriate actions in vehicle and relay this information through V2V or V2I within the vehicular network.
VANET users profit from many applications that are classified into active road safety, infotainment, traffic efficiency and management ; the latter stands for speed management and cooperative navigation.
The security is the state of being free from danger or threat. Security means safety, as well as the measures taken to be safe or protected. For example, in order to provide adequate security for the parade, town officials often hire extra guards.
In VANET, it is critical to guard against misuse activities and to well define the security architecture because it is a wireless communication which is harder to secure. The security and its guaranteed level of implementation affect people safety. Few years ago, many researchers have explored the security attacks and tried to find their related solutions. Others tried to define security in frastructures, or formalize standards and protocols. But still, the trend of trustworthiness of a node and misbehaving detection is large to explore.
This paper presents VANET security characteristics and investigates most of the VANET security challenges as well as the existing solutions in a comprehensive manner. After detailing the recent security architectures and the well-known security standards protocols, we present and discuss the recent frameworks that address the related issues. We focus on a novel classification of the different attacks known in the literature of VANET security and their solutions. Finally, despite all the promising opportunities that accompany VANET and after discussing the presented works, we have specified certain research challenges and open questions which may be future research directions. Thus enabling VANET to efficiently implement a system for trusting vehicles and protect it from malicious nodes.
The remainder of this paper is organized as follows: Section 2 expands VANET model and its security requirements. Section 3 details the attacker model. Section 4 presents the standardization efforts. Section 5 presents the solutions classified in a coherent manner. Section 6 expands the gap analysis. Section 7 highlights the emerging and open issues and we conclude in Section 8.
2. Vanet characteristics, security challenges and constraints
2.1. VANET characteristics
VANETs are ad hoc networks, highly dynamic, with little access to the network infrastructure and offering multiple services. The communication modes in VANET shown in Fig. 2 can be categorized into Vehicle to Vehicle (V2V), Vehicle to Infrastructure (V2I) and Hybrid. In V2V, the used communication media is characterized by short latency and high transmission rate. This architecture is used in different scenarios of broadcasting alerts (emergency braking, collision, deceleration, etc.) or in a cooperative driving. In V2I, vehicular network takes into account the applications that use the infrastructure points RSUs which multiply the services through internet portals in common. Hybrid mode is a combination of the two previous techniques. VANET characteristics explored in [1–6] can be grouped related to: i) Network topology and communication mode or ii) Vehicles and drivers.