Anonymous Authentication Protocols for Vehicular Ad Hoc Networks: An Overview <s> Security requirements <s> Privacy and security should be paid much more attention in secure vehicular ad hoc networks (VANETs). However, as far as we know, few researches on secure VANET protocols have addressed both the privacy issues and authenticated key establishment. Therefore, in this work, a lightweight authenticated key establishment scheme with privacy preservation to secure the communications between mobile vehicles and roadside infrastructure in a VANET is proposed, which is called SECSPP. Our proposed scheme not only accomplishes vehicle-to-vehicle and vehicle-to-roadside infrastructure authentication and key establishment for communication between members, but also integrates blind signature techniques into the scheme in allowing mobile vehicles to anonymously interact with the services of roadside infrastructure. We also show that our scheme is efficient in its implementation on mobile vehicles in comparison with other related proposals. <s> BIB001 </s> Anonymous Authentication Protocols for Vehicular Ad Hoc Networks: An Overview <s> Security requirements <s> VANETs have the potential to dramatically increase road safety by giving drivers more time to react adequately to dangerous situations. To prevent abuse of VANETs, a security infrastructure is needed that ensures security requirements like message integrity, confidentiality, and availability. After giving more details on the requirements we propose a security infrastructure that uses asymmetric as well as symmetric cryptography and tamper resistant hardware. While fulfilling the requirements, our proposal is especially designed to protect privacy of the VANET users and proves to be very efficient in terms of computational needs and bandwidth overhead. <s> BIB002 </s> Anonymous Authentication Protocols for Vehicular Ad Hoc Networks: An Overview <s> Security requirements <s> Vehicular networks are very likely to become the most pervasive and applicable of mobile ad hoc networks in this decade. Vehicular Ad hoc NETwork (VANET) has become a hot emerging research subject, but few academic publications describing its security infrastructure. In this paper, we review the secure infrastructure of VANET, some potential applications and interesting security challenges. To cope with these security challenges, we propose a novel secure scheme for vehicular communication on VANETs. The proposed scheme not only protects the privacy but also maintains the liability in the secure communications by using session keys. We also analyze the robustness of the proposed scheme. <s> BIB003 </s> Anonymous Authentication Protocols for Vehicular Ad Hoc Networks: An Overview <s> Security requirements <s> Vehicular ad hoc networks (VANETs) allow vehicle-to-vehicle communication and, in particular, vehicle-generated announcements. Provided that the trustworthiness of such announcements can be guaranteed, they can greatly increase the safety of driving. A new system for vehicle-generated announcements is presented that is secure against external and internal attackers attempting to send fake messages. Internal attacks are thwarted by using an endorsement mechanism based on threshold signatures. Our system outperforms previous proposals in message length and computational cost. Three different privacy-preserving variants of the system are also described to ensure that vehicles volunteering to generate and/or endorse trustworthy announcements do not have to sacrifice their privacy. <s> BIB004 </s> Anonymous Authentication Protocols for Vehicular Ad Hoc Networks: An Overview <s> Security requirements <s> Advances in wireless communications allow setting up communication links between vehicles for the exchange of information between them. Such vehicular ad hoc networks (VANETs) are important to enhance traffic safety since critical environmental conditions, such as road or traffic conditions, can be rapidly exchanged between vehicles in VANETs. However, to be useful for the driver, the information must be reliable, i.e., with great probability, the received information indeed reflects the actual situation. One approach to this is to regard information as reliable if it is confirmed by various sources. To achieve this, messages received must be distinguishable. This may become a threat against the privacy of drivers since by observing messages, vehicles may be traced. In this paper, we address the mentioned problems. We base the reliability of information on the number of different sources that confirmed specific information, and that number must be greater than a given threshold. We address the nontraceability by letting vehicles change their identity frequently. Our approach scales with respect to storage on the vehicle, as well as management of identities at a certification authority. <s> BIB005 </s> Anonymous Authentication Protocols for Vehicular Ad Hoc Networks: An Overview <s> Security requirements <s> Vehicular ad hoc networks (VANETs) are being designed to improve traffic safety and efficiency. To meet this goal, the messages disseminated in VANETs must be trustworthy. We propose a privacy-preserving system that guarantees message trustworthiness in vehicle-to-vehicle (V2V) communications. Vehicle privacy is provided as long as a vehicle does not attempt to endorse the same message more than once. In spite of a message having been validly endorsed, if it is later found to be false, the system offers the possibility of a posteriori tracing the message generator and its endorsers. Our proposal demonstrates a number of distinctive features. The system is equipped with both a priori and a posteriori countermeasures. The threshold used for a priori endorsement can adaptively change according to the message urgency and traffic context, rather than being preset in the system design stage as in existing schemes. The verification of authenticated V2V messages is accelerated by batch message-processing techniques. Simulation results illustrate that the system maintains its performance under various traffic conditions. <s> BIB006 </s> Anonymous Authentication Protocols for Vehicular Ad Hoc Networks: An Overview <s> Security requirements <s> Vehicular ad hoc networks (VANETs) allow wireless communications between vehicles without the aid of a central server. Reliable exchanges of information about road and traffic conditions allow a safer and more comfortable travelling environment. However, such profusion of information may allow unscrupulous parties to violate user privacy. On the other hand, a degree of auditability is desired for law enforcement and maintenance purposes. In this paper we propose a Threshold Anonymous Announcement service using direct anonymous attestation and one-time anonymous authentication to simultaneously achieve the seemingly contradictory goals of reliability, privacy and auditability. <s> BIB007
To countermeasure and mitigate the potential threats in the aforementioned attack models, a security system for safety messaging in a VANET should satisfy the following requirements. 1. Efficient anonymous authentication of safety messages: The security system should provide an efficient and anonymous message authentication mechanism. First of all, all accepted messages should be delivered unaltered, and the origin of the messages should be authenticated to guard against impersonation attacks. Meanwhile, from the point of vehicle owners, it may not be acceptable to leak personal information, including identity and location, to unauthorized observers while authenticating messages. Therefore, providing a secure yet anonymous message authentication is critical to the applicability of VANETs. Furthermore, considering the limited storage and computation resource of OBUs, the authentication scheme should have low overheads for safety message verification and storage. 2. Efficient tracking of the source of a disputed safety message: An important and challenging issue in these conditions is enabling a trusted third party (such as police officers) to retrieve a vehicle's real identity from its pseudo identity. If this feature is not provided, anonymous authentication can only prevent an outside attack, but cannot deal with an inside one. Furthermore, the system should not only provide safety message traceability to prevent inside attacks, but also have reasonable overheads for the revealing the identity of a message sender. BIB007 ; BIB004 ; BIB005 BIB006 : A message is viewed as trustworthy only after it has been endorsed by at least n vehicles, where n is a threshold. The threshold mechanism is a priori countermeasure that improves the confidence of other vehicles in a message. In addition, the threshold in the proposed scheme should be adaptive, that is to say, the sender can dynamically change the threshold according to the traffic context and scenarios. Kamat et al. (2006) ; BIB001 ; BIB002 ; BIB003 Some research teams pointed out that the privacy of the communication content should be protected against unauthorized observers. While confidentiality of communicating message can be negligible in most cases, it is e.g. crucial for services subject to costs. Besides application data administrative messages like routing protocol information or messages containing cryptographic material, the cryptographic information held by participants or centralized instances should also be protected against unauthorized access. • OBU: A vehicle can not join the VANETs unless it registers its own public system parameters and corresponding private key to the TA. The secret information such as private keys to be used generates the need for a tamper-proof device in each vehicle. According to existing works, only the authorized parties can access to this tamper-proof device. OBUs are mobile and moving most of the time. When the OBUs are on the road, they regularly broadcast routine safety messages, such as position, current time, direction, speed, traffic conditions, traffic events. The information system on each vehicle aggregates and diffuses these messages to enable drivers form a better awareness of their environment (Fig. 2) . The assumed communication protocol between neighboring OBUs (IVC) or between an OBU and a RSU (V2I) is 5.9 GHz Dedicated Short Range Communication (DSRC) DSRC (1999) IEEE 802.11p.