A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Group Signature Schemes <s> Existing authentication protocols to secure vehicular ad hoc networks (VANETs) raise challenges such as certificate distribution and revocation, avoidance of computation and communication bottlenecks, and reduction of the strong reliance on tamper-proof devices. This paper efficiently copes with these challenges with a decentralized group-authentication protocol in the sense that the group is maintained by each roadside unit (RSU) rather than by a centralized authority, as in most existing protocols that are employing group signatures. In our proposal, we employ each RSU to maintain and manage an on-the-fly group within its communication range. Vehicles entering the group can anonymously broadcast vehicle-to-vehicle (V2V) messages, which can be instantly verified by the vehicles in the same group (and neighboring groups). Later, if the message is found to be false, a third party can be invoked to disclose the identity of the message originator. Our protocol efficiently exploits the specific features of vehicular mobility, physical road limitations, and properly distributed RSUs. Our design leads to a robust VANET since, if some RSUs occasionally collapse, only the vehicles that are driving in those collapsed areas will be affected. Due to the numerous RSUs sharing the load to maintain the system, performance does not significantly degrade when more vehicles join the VANET; hence, the system is scalable. <s> BIB001 </s> A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Group Signature Schemes <s> Although lots of research efforts have focused on group key management (GKM) for secure multicast, existing GKM schemes are inadequate for vehicle communication (VC) systems since they incur unnecessary rekeying overhead without considering the characteristics of VC systems such as Vehicle-to-Infrastructure communications and a great number of high mobility vehicles. Therefore, we propose a GKM scheme, called RSU-based decentralized key management (RDKM), dedicated for the multicast services in the VC systems. The RDKM scheme significantly reduces the rekeying overhead through delegating a part of the key management functions to the road-side infrastructure units (RSUs) and through updating the key encryption keys (KEKs) within a RSU. The performance of the RDKM scheme is analyzed in terms of communication overhead and storage overhead each of which has a strong impact on the performance of GKM. Furthermore, we propose an optimization algorithm that minimizes the weighted sum of the communication and the storage overhead, called the GKM overhead (GKMO), by appropriately determining the design parameters. The numerical results from the extensive analysis demonstrate that the RDKM scheme outperforms the existing GKM schemes in terms of the GKMO. <s> BIB002 </s> A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Group Signature Schemes <s> Group signature is one of the well-known cryptographic primitives for anonymous authentication which is the fundamental requirement for securing vehicular ad hoc networks (VANETs), but it is prone to cause huge revocation overhead in VANETs with millions of nodes and serious security risk. To solve this problem, we develop an efficient distributed key management scheme (DKM) where the whole domain of VANET is divided into several sub-regions, and any vehicle has to update its group secret key periodically from the regional group manager who manages the region where the vehicle stays. Unlike the previously reported works, DKM prevents vehicles from leaking the value of the updated group secret key to the regional group manager during the group key updating process. Subsequently, it is capable of identifying either the compromised regional authorities or the malicious vehicles. Moreover, performance analysis demonstrates that DKM can reduce the revocation cost significantly while the communication cost for key updating is small. Copyright © 2011 John Wiley & Sons, Ltd. <s> BIB003 </s> A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Group Signature Schemes <s> In ad hoc wireless networks like Vehicular ad hoc Network (VANETs) or Wireless Sensor Networks (WSN), data confidentiality is usually a minor requirement contrary to data authenticity and integrity. Messages broadcasted from a node to other nodes should be authentic but also keep user's privacy in plenty scenarios working with personal data. Group signatures (GS) are used to provide privacy and authenticity to the users. Moreover, GS with batch verification can be efficient. Nevertheless, the current solutions have practical drawbacks like using an expensive tamper-proof hardware, the computation bottlenecks of the verification and revocation phases, complicated certificate distribution/revocation or omitting important properties like short-term linkability which is demanded in several applications, e.g. change lanes of vehicles in VANETs. To our best knowledge, our solution employs the short group signature with short-term linkability and categorized batch verification for the first time. Our solution provides more efficient signing and verification than compared schemes. Moreover, the solution allows secure and practical registration and revocation of users. The usage of proposed scheme protects the honest users who can now join and securely communicate without losing their privacy. <s> BIB004 </s> A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Group Signature Schemes <s> Vehicular ad hoc networks (VANETs) have stimulated interest in both academic and industry settings because, once deployed, they would bring a new driving experience to drivers. However, communicating in an open-access environment makes security and privacy issues a real challenge, which may affect the large-scale deployment of VANETs. Researchers have proposed many solutions to these issues. We start this paper by providing background information of VANETs and classifying security threats that challenge VANETs. After clarifying the requirements that the proposed solutions to security and privacy problems in VANETs should meet, on the one hand, we present the general secure process and point out authentication methods involved in these processes. Detailed survey of these authentication algorithms followed by discussions comes afterward. On the other hand, privacy preserving methods are reviewed, and the tradeoff between security and privacy is discussed. Finally, we provide an outlook on how to detect and revoke malicious nodes more efficiently and challenges that have yet been solved. <s> BIB005 </s> A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Group Signature Schemes <s> Advances in mobile networking and information processing technologies have triggered vehicular ad hoc networks (VANETs) for traffic safety and value-added applications. Most efforts have been made to address the security concerns while little work has been done to investigate security and privacy for value-added applications in VANETs. To fill this gap, we propose a secure and privacy-preserving scheme for value-added applications in VANETs; specifically, a vehicular secure and privacy-preserving location-based service (LBS). For each LBS transaction, the scheme provides authentication, integrity and non-repudiation for both the service provider and the vehicle. A vehicle can obtain the service in an anonymous way and hence vehicle privacy is well protected. However, if a vehicle maliciously uses the service, a tracing procedure can be invoked to find the malicious vehicle, thereby efficiently preventing vehicles from abusing the anonymity provided by the system. These features are achieved by efficiently exploiting the available infrastructure of VANETs and without requiring cooperation from other vehicles, which might be reluctant to cooperate or otherwise unavailable. Although public-key cryptosystems are employed as building blocks, no complicated certificate management is required by our system. <s> BIB006 </s> A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Group Signature Schemes <s> Abstract With the rapid growth of information and communication technology (ICT) and Internet of things (IoT), the concept of smart-city is recently introduced by the government of many countries to improve the living environment of urban people. In city areas, the numbers of vehicles are increased exponentially day-by-day. Therefore, it is very difficult to control and manage the city traffic caused by tens of thousands vehicles. The Vehicular Ad-hoc Network (VANET) is used to communicate with the vehicles to give alert for weather conditions, road defects, traffic conditions, etc. and the conditions of the vehicle including location, speed, traffic status, etc. Therefore, the traffic efficiency and safety of the vehicles can be improved with the help of VANET. To serve this purpose, in the literature, many conditional privacy preserving authentication (CPPA) protocols based on CA-PKC (certificate authority-based public key cryptography), and ID-PKC (identity-based public key cryptography) have been put forwarded. In addition, some of these CPPA protocols use elliptic curve or bilinear-pairing for their implementation. The computation cost for bilinear-pairing and elliptic curve is very high compared to the cryptographic general hash function. Therefore, all the earlier protocols suffer from the heavy computational burden and some security weaknesses as well. Therefore, bilinear-pairing-free, robust and efficient CPPA with group-key agreement protocol for VANETs is essential. This paper presents a password-based conditional privacy preserving authentication and group-key generation (PW-CPPA-GKA) protocol for VANETs. Our protocol offers group-key generation, user leaving, user join, and password change facilities. Our protocol is lightweight in terms computation and communication since it can be designed without bilinear-pairing and elliptic curve. <s> BIB007
The vehicle privacy is preserved in the group signature based schemes, which can allow registered members of the group to sign up for the messages anonymously as a representative of the group BIB005 . The head of the group has the right to find out which sign is coming from the original sender. The group signature usually requires a large amount of time to verify the signature, which makes it limited to time-related applications in VANETs. In 2010, Zhang et al. BIB001 proposed an efficient method that utilized each RSU to maintain and managed on-the-fly group within its range of communication, and the vehicles, which enter the group and can secretly send V2V messages. These can be further verified by users of the same group, if any bogus message produced by the vehicle can be traced by the trusted authority. In 2011, Park et al. BIB002 presented an RSU-based decentralized key management (RDKM), which is used only for multicast services in vehicle communication (VC) systems. This scheme reduced the large amount of rekeying overhead by contributing some portion of the key management functions to the RSUs and also by updating the key encryption keys (KEKs) within the RSUs. To alleviate the overhead of revocation, the distributed management system is a promising approach. Based on this technique in 2012, Sun et al. BIB003 introduced a distributed key management system (DKM) in the VANET system. In this scheme, the domain is formed into small sub-regions, and the vehicle needed to update it is the secret key from the regional head of the group, which manages the region. In this approach, during the updating process, the DKM restricts the vehicle to disclose the updated value of a secret key to the regional head of the group. However, the anonymity feature of the group signature makes it vulnerable to attack by a malicious user through the broadcasting of fake messages. Malina et al. BIB004 introduced a group signature with short-term linkability and categorized the batch verification. This method produced efficient signing and verification as compared to other competent methods. In Reference BIB006 , Zhang et al. introduced a location based service (LBS) protocol, which is used to address the inherent challenges in terms of authentication and conditional privacy for offering LBSs in VANETs. In this scheme, the providers of RSUs and LBS are identity-based, and a vehicle only requires a member key. By using this key vehicle, it can generate verifier-location group signatures. The LBS validates these signatures without interfering the privacy of a vehicle. If an LBS request is found to be false, then the key generation certificate can evaluate the vehicle ID. Islam et al. BIB007 introduced a password-based conditional privacy preserving authentication and group-key generation (PW-CPPA-GKA) protocol for the VANET system. This method provides several features such as user exiting, user entering, and changing a password. This protocol is computationally stable since it is designed without using bilinear pairing and elliptic curve techniques.