A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Challenge on Security <s> Recently, security and privacy have been one of the main concerns that impedes the development of vehicular ad hoc networks (VANETs). In this paper, we put forward an access control with authentication scheme for disseminated messages in VANETs. In the scheme, we integrate pseudonym with identity based signature (IBS) which could not only authenticate the messages in vehicular communication, but also protect the privacy of message generators. When vehicles receive numerous messages that need to be authenticated in a short time, we also apply batch verification to improve the efficiency of message disseminating. Then we adopt ciphertext policy attribute based encryption (CP-ABE), which provides access control service to set expressive and flexible access structure for the specified vehicles in VANETs communication. The experimental results show that the proposed scheme is efficient in message authentication and access control for vehicular communication in VANETs. <s> BIB001 </s> A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Challenge on Security <s> In vehicular ad hoc networks (VANETs), when a vehicle receives a message, the certificate revocation list (CRL) checking process will operate before certificate and signature verification. However, large communication sources, storage space, and checking time are needed for CRLs that cause the privacy disclosure issue as well. To address these issues, in this paper, we propose an efficient anonymous batch authentication scheme (ABAH) to replace the CRL checking process by calculating the hash message authentication code (HMAC). In our scheme, we first divide the precinct into several domains, in which road-side units (RSUs) manage vehicles in a localized manner. Then, we adopt pseudonyms to achieve privacy-preserving and realize batch authentication by using an identity-based signature (IBS). Finally, we use HMAC to avoid the time-consuming CRL checking and to ensure the integrity of messages that may get loss in previous batch authentication. The security and performance analysis are carried out to demonstrate that ABAH is more efficient in terms of verification delay than the conventional authentication methods employing CRLs. Meanwhile, our solution can keep conditional privacy in VANETs. <s> BIB002 </s> A Survey of Security Services, Attacks, and Applications for Vehicular Ad Hoc Networks (VANETs) <s> Challenge on Security <s> Providing an efficient anonymous authentication scheme in vehicular ad hoc networks (VANETs) with low computational cost is a challenging issue. Even though, there are some existing schemes to provide anonymous authentication, the existing schemes suffer from high computational cost in the certificate and the signature verification process, which leads to high message loss. Therefore, they fail to meet the necessity of verifying hundreds of messages per second in VANETs. In our scheme, we propose an efficient anonymous authentication scheme to avoid malicious vehicles entering into the VANET. In addition, the proposed scheme offers a conditional tracking mechanism to trace the vehicles or roadside units that abuse the VANET. As a result, our scheme revokes the privacy of misbehaving vehicles to provide conditional privacy in a computationally efficient way through which the VANET entities will be anonymous to each other until they are revoked from the VANET system. Moreover, the proposed scheme is implemented and the performance analysis shows that our scheme is computationally efficient with respect to the certificate and the signature verification process by keeping conditional privacy in VANETs. <s> BIB003
Since the communication takes place in an open access environment, which make VANETs more vulnerable to attacks that cause multiple threats to the security services. In particular, a Sybil attack is one of the most dangerous attacks in VANETs. This attack is the most influential attack that is addressed by the researchers. Maintaining the balance between privacy and non-repudiation is still required in order to detect Sybil attacks. In the past, many studies have been done on Sybil attacks. On the other hand, many other attacks such as jamming attacks and malware attacks in VANETs motivate further research. Many security challenges still exist, which need superior algorithms in order to solve these challenges. A robust authentication technique along with the message exchange approach is used to protect V2I and V2V communications from inside and outside attackers. The main problem occurs when the utilization of CA and TA and the schemes that rely on the private keys for V2X, i.e., V2V and V2I communications, can protect the vehicular network. However, it can increase the computational and transmission overheads and introduce the scalability challenges. Kang et al. BIB001 presented an access control technique for message broadcasting in VANETs, which aim to protect the message privacy. However, this scheme did not consider communication overhead and the delay occurred in the verification process. Wasef and Shen  introduced an EMAP technique for VANETs. This scheme alleviated the large computational process of CRL by an effective revocation process. This scheme significantly reduced the authentication delay. However, this scheme did not consider the communication overhead and cost occurred during the authentication process. In Reference BIB003 , Azees et al. introduced an EAAP scheme to avoid a malicious vehicle from entering in VANETs. However, in this scheme, the signature verification can produce a delay in the verification process. Jiang et al. BIB002 introduced an efficient anonymous batch verification technique. This scheme somehow improves the efficiency of VANETs by utilizing the hash message authentication code (HMAC). However, it increases the packet loss. More specifically, VANET security remains a challenging issue, in which the authentication scheme plays an important role for tackling all kinds of threats and attacks. In this context, we still need an efficient authentication scheme, i.e., message authentication to protect the V2V and V2I communications.