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Academic Editor:Michele Amoretti
School of Computer Science and Technology, Nantong University, Nantong 226019, China
Received 8 November 2015; Revised 12 February 2016; Accepted 14 February 2016
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
A vehicular ad hoc network (VANET) typically consists of roadside infrastructure and vehicles that are connected in a self-organized way. It supports safety applications, convenience applications, and commercial applications, such as collision warning, congested road notification, and infotainment. These applications are highly dependent on the liable messages generated by vehicles. Because false messages may lead to failures, injuries, and even deaths, false information should not be transferred by the neighbor node which affects the overall performance of network [1]. Traditional network security approaches such as the use of firewall, access control, and authorized certification are greatly investigated to secure VANETs. These approaches, known as hard security mechanisms [2], are very effective in protecting VANETs from external attackers. However, what if some internal attackers (the vehicles with true legal IDs) intentionally produce false messages to cheat others? For example, a malicious internal vehicle may send a false congestion warning to let other vehicles make unnecessary detours. In such case, the validation of a sender's ID cannot guarantee the truth of the message. A potential way to address such problems is using trust management [3], which are also known as soft security mechanisms [2].
1.1. Motivation
There have already been many reputation systems proposed for other environments, such as peer-to-peer networks [4], ad hoc networks [5], and wireless sensor networks [6]. However, these reputation systems are not feasible for VANETs because they do not concern the characteristics of VANETs, such as high dynamics and privacy concerns. Recently, some trust management systems [7-14] have been proposed for VANETs. However, they have two drawbacks.
First, these trust management systems may be vulnerable to tactical attacks. In the preliminary stage, the trust management systems in VANETs are designed to deal with the basic attack-lying, in which the liars send false service messages individually. However, when realizing the effect of trust management systems incorporated into the VANET, the malicious vehicles are likely to...