Safety-critical applications in cooperative vehicular networks require authentication of nodes and messages. Yet, privacy of individual vehicles and drivers must be maintained. Pseudonymity can satisfy both security and privacy requirements. Thus, a large body of work emerged in recent years, proposing pseudonym solutions tailored to vehicular networks. In this survey, we detail the challenges and requirements for such pseudonym mechanisms, propose an abstract pseudonym lifecycle, and give an extensive overview and categorization of the state of the art in this research area. Specifically, this survey covers pseudonym schemes based on public key and identity-based cryptography, group signatures and symmetric authentication. We compare the different approaches, give an overview of the current state of standardization, and identify open research challenges.

Vehicular networking enables new safety applications that aim at improving roads safety. Because of their direct relation to driver's safety, this goal can only be achieved if vehicular networking is based on a technology that is robust against malicious attackers. Therefore, security mechanisms such as authentication are proposed. However, security comes at a cost in terms of computational and communication overhead. For example, a signature and certificate are appended to every beacon sent, which generates an extra load on the network. Moreover, most of the safety applications require a perfect awareness of the vehicle's surroundings to perform adequately. To represent such awareness, the Awareness Quality is used to indicate the current level of awareness of the vehicle. This metric was previously used by the Decentralized Congestion Control community to improve channel usage. In this paper, we use the Awareness Quality to investigate the impact of security on cooperative awareness in VANET. Then, we apply this metric to the mechanism of certificate omission, and provide extensive simulation results. The attributes of Awareness Quality metrics enable us to investigate the behavior of certificate omission schemes with a precision that was not provided by aggregate metrics. This enables us to show that congestion-based certificate omission with a quadratic adaption function is the most effective scheme among existing certificate omission schemes.

Telematic awareness of nearby vehicles is a basic foundation of electronic safety applications in Vehicular Ad hoc Networks (VANETs). This awareness is achieved by frequently broadcasting beacon messages to nearby vehicles that announce a vehicle's location and other data like heading and speed. Such safety-related beacons require strong integrity protection and high reliability, two properties that are hard to combine because the communication and computation overhead introduced by security mechanisms affects reliability. This applies especially to the signatures and certificates needed for authentication. We propose a mechanism to reduce the communication overhead of secure safety beacons by adaptively omitting the inclusion of certificates in messages. In contrast to similar earlier proposals, we control the omission rate based on estimated channel congestion. A simulation study underlines the advantages of the congestion-based certificate omission scheme compared to earlier approaches. Moreover, we show that the benefits of certificate omission outweigh the negative effect of cryptographically unverifiable beacons.

Because of the potential impact on user's life in cooperative automated safety applications, the security of Vehicleto-X communication (V2X) is mandatory. However, the current attacker model used in literature is often too network-oriented, and it is unclear what realistic attacks could be. In this paper, we use the V2X data lifecycle to derive the attack surfaces. From this, we lay the foundations of a revisited attacker model, which details realistic attacks and identify appropriate countermeasures. We demonstrate that while the security of data processing, data at rest, and data in-transit is well-advanced, the security of metadata and data acquisition requires extra attention by the research community.

Vehicular ad hoc networks aim at enhancing road safety by providing vehicle-to-vehicle communications and safetyrelated applications. But safety-related applications, like Local Danger Warning, need a high trust level in received messages. Indeed, decisions are made depending on these messages. To increase the trustworthiness, a consensus mechanism is used. Thus, vehicles make a decision when a threshold is reached. Setting this threshold is of main importance because it impacts the decision delay, and thus, the remaining time for a driver reaction. In this paper, we investigate the problem of threshold establishment without globally unique identifier system (GUID). We propose to model the threshold as a Kalman filter and provide an algorithm to dynamically update the threshold. By simulations, we investigate the problem of insider attackers that generate information forgery attacks. Simulation results show that our dynamic method suffers from a bootstrapping phase but reduces the percentage of wrong decisions. Nevertheless, as future work, further analysis of default threshold value will be done.