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Hamdi, Mustafa Maad, Yussen, Yuser Anas, Mustafa, Ahmed Shamil.  2021.  Integrity and Authentications for service security in vehicular ad hoc networks (VANETs): A Review. 2021 3rd International Congress on Human-Computer Interaction, Optimization and Robotic Applications (HORA). :1–7.
A main type of Mobile Ad hoc Networks (MANET) and essential infrastructure to provide a wide range of safety applications to passengers in vehicles (VANET) are established. VANETs are more popular today as they connect to a variety of invisible services. VANET protection is crucial as its potential use must not endanger the safety and privacy of its users. The safety of these VANETs is essential to safe and efficient safety systems and facilities and uncertainty continues and research in this field continues to grow rapidly. We will explain the characteristics and problems of VANETs in this paper. Also, all threats and attacks that affect integrity and authentication in VANETs will be defined. Description of researchers' work was consequently addressed as the table with the problems of the suggested method and objective.
Acharya, Abiral, Oluoch, Jared.  2021.  A Dual Approach for Preventing Blackhole Attacks in Vehicular Ad Hoc Networks Using Statistical Techniques and Supervised Machine Learning. 2021 IEEE International Conference on Electro Information Technology (EIT). :230–235.
Vehicular Ad Hoc Networks (VANETs) have the potential to improve road safety and reduce traffic congestion by enhancing sharing of messages about road conditions. Communication in VANETs depends upon a Public Key Infrastructure (PKI) that checks for message confidentiality, integrity, and authentication. One challenge that the PKI infrastructure does not eliminate is the possibility of malicious vehicles mounting a Distributed Denial of Service (DDoS) attack. We present a scheme that combines statistical modeling and machine learning techniques to detect and prevent blackhole attacks in a VANET environment.Simulation results demonstrate that on average, our model produces an Area Under The Curve (ROC) and Receiver Operating Characteristics (AUC) score of 96.78% which is much higher than a no skill ROC AUC score and only 3.22% away from an ideal ROC AUC score. Considering all the performance metrics, we show that the Support Vector Machine (SVM) and Gradient Boosting classifier are more accurate and perform consistently better under various circumstances. Both have an accuracy of over 98%, F1-scores of over 95%, and ROC AUC scores of over 97%. Our scheme is robust and accurate as evidenced by its ability to identify and prevent blackhole attacks. Moreover, the scheme is scalable in that addition of vehicles to the network does not compromise its accuracy and robustness.
R, Naveen, Chaitanya, N.S.V, M, Nikhil Srinivas, Vineeth, Nandhini.  2020.  Implementation of a Methodology for Detection and Prevention of Security Attacks in Vehicular Adhoc Networks. 2020 IEEE International Conference for Innovation in Technology (INOCON). :1–6.
In the current generation, road accidents and security problems increase dramatically worldwide in our day to day life. In order to overcome this, Vehicular Ad-hoc Network (VANETs) is considered as a key element of future Intelligent Transportation Systems (ITS). With the advancement in vehicular communications, the attacks have also increased, and such architecture is still exposed to many weaknesses which led to numerous security threats that must be addressed before VANET technology is practically and safely adopted. Distributed Denial of Service (DDoS) attack, replay attacks and Sybil attacks are the significant security threats that affect the communication and privacy in VANET. An algorithm to detect and prevent various kinds of security attacks in VANET communication has been designed and proposed in this work. An analysis has also been done by applying four protocols on an existing scenario of real traffic simulator using OpenStreetMap and the best suitable protocol has been selected for further application. The evaluation has been done using SUMO, NS3 and Java simulation environment. Simulation results and extensive performance analysis shows that our proposed Algorithm performs well in detecting and preventing the attacks in VANET communication.
Zhang, H., Zhang, D., Chen, H., Xu, J..  2020.  Improving Efficiency of Pseudonym Revocation in VANET Using Cuckoo Filter. 2020 IEEE 20th International Conference on Communication Technology (ICCT). :763–769.
In VANETs, pseudonyms are often used to replace the identity of vehicles in communication. When vehicles drive out of the network or misbehave, their pseudonym certificates need to be revoked by the certificate authority (CA). The certificate revocation lists (CRLs) are usually used to store the revoked certificates before their expiration. However, using CRLs would incur additional storage, communication and computation overhead. Some existing schemes have proposed to use Bloom Filter to compress the original CRLs, but they are unable to delete the expired certificates and introduce the false positive problem. In this paper, we propose an improved pseudonym certificates revocation scheme, using Cuckoo Filter for compression to reduce the impact of these problems. In order to optimize deletion efficiency, we propose the concept of Certificate Expiration List (CEL) which can be implemented with priority queue. The experimental results show that our scheme can effectively reduce the storage and communication overhead of pseudonym certificates revocation, while retaining moderately low false positive rates. In addition, our scheme can also greatly improve the lookup performance on CRLs, and reduce the revocation operation costs by allowing deletion.
Quevedo, C. H. O. O., Quevedo, A. M. B. C., Campos, G. A., Gomes, R. L., Celestino, J., Serhrouchni, A..  2020.  An Intelligent Mechanism for Sybil Attacks Detection in VANETs. ICC 2020 - 2020 IEEE International Conference on Communications (ICC). :1–6.
Vehicular Ad Hoc Networks (VANETs) have a strategic goal to achieve service delivery in roads and smart cities, considering the integration and communication between vehicles, sensors and fixed road-side components (routers, gateways and services). VANETs have singular characteristics such as fast mobile nodes, self-organization, distributed network and frequently changing topology. Despite the recent evolution of VANETs, security, data integrity and users privacy information are major concerns, since attacks prevention is still open issue. One of the most dangerous attacks in VANETs is the Sybil, which forges false identities in the network to disrupt compromise the communication between the network nodes. Sybil attacks affect the service delivery related to road safety, traffic congestion, multimedia entertainment and others. Thus, VANETs claim for security mechanism to prevent Sybil attacks. Within this context, this paper proposes a mechanism, called SyDVELM, to detect Sybil attacks in VANETs based on artificial intelligence techniques. The SyDVELM mechanism uses Extreme Learning Machine (ELM) with occasional features of vehicular nodes, minimizing the identification time, maximizing the detection accuracy and improving the scalability. The results suggest that the suitability of SyDVELM mechanism to mitigate Sybil attacks and to maintain the service delivery in VANETs.
Ma, Y., Bai, X..  2019.  Comparison of Location Privacy Protection Schemes in VANETs. 2019 12th International Symposium on Computational Intelligence and Design (ISCID). 2:79–83.
Vehicular Ad-hoc Networks (VANETs) is a traditional mobile ad hoc network (MANET) used on traffic roads and it is a special mobile ad hoc network. As an intelligent transportation system, VANETs can solve driving safety and provide value-added services. Therefore, the application of VANETs can improve the safety and efficiency of road traffic. Location services are in a crucial position for the development of VANETs. VANETs has the characteristics of open access and wireless communication. Malicious node attacks may lead to the leakage of user privacy in VANETs, thus seriously affecting the use of VANETs. Therefore, the location privacy issue of VANETs cannot be ignored. This paper classifies the attack methods in VANETs, and summarizes and compares the location privacy protection techniques proposed in the existing research.
Kaur, Jasleen, Singh, Tejpreet, Lakhwani, Kamlesh.  2019.  An Enhanced Approach for Attack Detection in VANETs Using Adaptive Neuro-Fuzzy System. 2019 International Conference on Automation, Computational and Technology Management (ICACTM). :191—197.
Vehicular Ad-hoc Networks (VANETs) are generally acknowledged as an extraordinary sort of Mobile Ad hoc Network (MANET). VANETs have seen enormous development in a decade ago, giving a tremendous scope of employments in both military and in addition non-military personnel exercises. The temporary network in the vehicles can likewise build the driver's capability on the road. In this paper, an effective information dispersal approach is proposed which enhances the vehicle-to-vehicle availability as well as enhances the QoS between the source and the goal. The viability of the proposed approach is shown with regards to the noteworthy gets accomplished in the parameters in particular, end to end delay, packet drop ratio, average download delay and throughput in comparison with the existing approaches.
Kumar, Sushil, Mann, Kulwinder Singh.  2019.  Prevention of DoS Attacks by Detection of Multiple Malicious Nodes in VANETs. 2019 International Conference on Automation, Computational and Technology Management (ICACTM). :89—94.

Vehicular Adhoc Network (VANET), a specialized form of MANET in which safety is the major concern as critical information related to driver's safety and assistance need to be disseminated between the vehicle nodes. The security of the nodes can be increased, if the network availability is increased. The availability of the network is decreased, if there is Denial of Service Attacks (DoS) in the network. In this paper, a packet detection algorithm for the prevention of DoS attacks is proposed. This algorithm will be able to detect the multiple malicious nodes in the network which are sending irrelevant packets to jam the network and that will eventually stop the network to send the safety messages. The proposed algorithm was simulated in NS-2 and the quantitative values of packet delivery ratio, packet loss ratio, network throughput proves that the proposed algorithm enhance the security of the network by detecting the DoS attack well in time.

Sattar, Muhammad Umar, Rehman, Rana Asif.  2019.  Interest Flooding Attack Mitigation in Named Data Networking Based VANETs. 2019 International Conference on Frontiers of Information Technology (FIT). :245—2454.

Nowadays network applications have more focus on content distribution which is hard to tackle in IP based Internet. Information Centric Network (ICN) have the ability to overcome this problem for various scenarios, specifically for Vehicular Ad Hoc Networks (VANETs). Conventional IP based system have issues like mobility management hence ICN solve this issue because data fetching is not dependent on a particular node or physical location. Many initial investigations have performed on an instance of ICN commonly known as Named Data Networking (NDN). However, NDN exposes the new type of security susceptibilities, poisoning cache attack, flooding Interest attack, and violation of privacy because the content in the network is called by the name. This paper focused on mitigation of Interest flooding attack by proposing new scheme, named Interest Flooding Attack Mitigation Scheme (IFAMS) in Vehicular Named Data Network (VNDN). Simulation results depict that proposed IFAMS scheme mitigates the Interest flooding attack in the network.

Tahir, Muhammad Usman, Rehman, Rana Asif.  2018.  CUIF: Control of Useless Interests Flooding in Vehicular Named Data Networks. 2018 International Conference on Frontiers of Information Technology (FIT). :303–308.
Now-a-days vehicular information network technology is receiving a lot of attention due to its practical as well as safety related applications. By using this technology, participating vehicles can communicate among themselves on the road in order to obtain any interested data or emergency information. In Vehicular Ad-Hoc Network (VANET), due to the fast speed of the vehicles, the traditional host centric approach (i.e. TCP/IP) fails to provide efficient and robust communication between large number of vehicles. Therefore, Named Data Network (NDN) newly proposed Internet architecture is applied in VANET, named as VNDN. In which, the vehicles can communicate with the help of content name rather than vehicle address. In this paper, we explored the concepts and identify the main packet forwarding issues in VNDN. Furthermore, we proposed a protocol, named Control of Useless Interests Flooding (CUIF) in Vehicular Named Data Network. In which, it provides the best and efficient communication environment to users while driving on the highway. CUIF scheme reduces the Interest forwarding storm over the network and control the flooding of useless packets against the direction of a Producer vehicle. Our simulation results show that CUIF scheme decreases the number of outgoing Interest packets as well as data download time in the network.
Fouchal, Hacène, Ninet, Alain.  2020.  Partial Signature for Cooperative Intelligent Transport Systems. 2020 International Conference on Computing, Networking and Communications (ICNC). :586–590.
On C-ITS (Cooperative Intelligent Transport Systems) vehicles send and receive sensitive messages informing about events on roads (accidents, traffic jams, etc,..). The authentication of these messages is highly recommended in order to increase the users confidence about this system. This authentication ensures that only messages coming from trusted vehicles are accepted by receivers. An adapted PKI (Public Key Infrastructure) for C-ITS provides certificates for each vehicle. The certificate will be used to sign messages. This principle is used within deployed C-ITS solutions over the world. This solution is easy to implement but has one major flaw: each message needs to be sent with its signature and its certificate. The size of the message to send becomes high. In the meantime, for many C-ITS use cases, each message is sent many times for robustness reasons. The communication channel could be overloaded. In this paper, we propose to split the signature into some equal parts. When a message has to be sent, it will be sent with one of these parts. A receiver will save the received message with its actual part. For each reception, it will collect the remaining signature parts until all the signature parts are received. Our solution is implemented in a C-ITS architecture working through Bluetooth protocol using the advertising model. The solution is applicable for vehicle speeds reaching 130 km/h. We have proved, through a set of real experimentations, that our solution is possible.
Lai, Chengzhe, Ding, Yuhan.  2019.  A Secure Blockchain-Based Group Mobility Management Scheme in VANETs. 2019 IEEE/CIC International Conference on Communications in China (ICCC). :340–345.

Vehicular Ad-hoc Network (VANET) can provide vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communications for efficient and safe transportation. The vehicles features high mobility, thus undergoing frequent handovers when they are moving, which introduces the significant overload on the network entities. To address the problem, the distributed mobility management (DMM) protocol for next generation mobile network has been proposed, which can be well combined with VANETs. Although the existing DMM solutions can guarantee the smooth handovers of vehicles, the security has not been fully considered in the mobility management. Moreover, the most of existing schemes cannot support group communication scenario. In this paper, we propose an efficient and secure group mobility management scheme based on the blockchain. Specifically, to reduce the handover latency and signaling cost during authentication, aggregate message authentication code (AMAC) and one-time password (OTP) are adopted. The security analysis and the performance evaluation results show that the proposed scheme can not only enhance the security functionalities but also support fast handover authentication.

Malik, Nisha, Nanda, Priyadarsi, He, Xiangjian, Liu, RenPing.  2019.  Trust and Reputation in Vehicular Networks: A Smart Contract-Based Approach. 2019 18th IEEE International Conference On Trust, Security And Privacy In Computing And Communications/13th IEEE International Conference On Big Data Science And Engineering (TrustCom/BigDataSE). :34–41.
Appending digital signatures and certificates to messages guarantee data integrity and ensure non-repudiation, but do not identify greedy authenticated nodes. Trust evolves if some reputable and trusted node verifies the node, data and evaluates the trustworthiness of the node using an accurate metric. But, even if the verifying party is a trusted centralized party, there is opacity and obscurity in computed reputation rating. The trusted party maps it with the node's identity, but how is it evaluated and what inputs derive the reputation rating remains hidden, thus concealment of transparency leads to privacy. Besides, the malevolent nodes might collude together for defamatory actions against reliable nodes, and eventually bad mouth these nodes or praise malicious nodes collaboratively. Thus, we cannot always assume the fairness of the nodes as the rating they give to any node might not be a fair one. In this paper, we propose a smart contract-based approach to update and query the reputation of nodes, stored and maintained by IPFS distributed storage. The use case particularly deals with an emergency scenario, dealing against colluding attacks. Our scheme is implemented using MATLAB simulation. The results show how smart contracts are capable of accurately identifying trustworthy nodes and record the reputation of a node transparently and immutably.
Guleria, Charu, Verma, Harsh Kumar.  2018.  Improved Detection and Mitigation of DDoS Attack in Vehicular ad hoc Network. 2018 4th International Conference on Computing Communication and Automation (ICCCA). :1–4.
Vehicular ad hoc networks (VANETs) are eminent type of Mobile ad hoc Networks. The network created in VANETs is quite prone to security problem. In this work, a new mechanism is proposed to study the security of VANETs against DDoS attack. The proposed mechanism focuses on distributed denial of service attacks. The main idea of the paper is to detect the DDoS attack and mitigate it. The work consists of two stages, initially attack topology and network congestion is created. The second stage is to detect and mitigate the DDoS attack. The existing method is compared with the proposed method for mitigating DDoS attacks in VANETs. The existing solutions presented by the various researchers are also compared and analyzed. The solution for such kind of problem is provided which is used to detect and mitigate DDoS attack by using greedy approach. The network environment is created using NS-2. The results of simulation represent that the proposed approach is better in the terms of network packet loss, routing overhead and network throughput.
Achichi, Boubakeur, Semchedine, Fouzi, Derdouri, Lakhdar.  2018.  Hybrid Approach for Congestion Control in VANETs. Proceedings of the 7th International Conference on Software Engineering and New Technologies. :4:1-4:4.

Vehicular Ad-Hoc Network, or VANETs, is a form of MANET, through which cars will exchange messages to detect dangerous situations and announce them to drivers. In VANETs, vehicles (nodes) are characterized by a high dynamics and high mobility, in addition to the high rate of topology change and density variability. Quality of service in VANETs represents a major challenge, not yet solved, due to the characteristics and strict constraints of VANETs. In order to improve the performance and reliability of message dissemination on VANETs, congestion control must be taken into account. Many studies asserted that proper congestion control algorithms are essential to ensure an efficient network operation. However, most of the existing congestion control solutions have limitations. In this paper, we propose congestion control algorithm as solution to avoid congestion in VANETs environment. The proposed solution is based on a combination of two approaches: the event-oriented and the measurement-based, with message scheduling. The proposed solution is to reduce congestion and increase reliability to VANETs by assigning higher priority to critical security message.

Iwendi, C., Uddin, M., Ansere, J. A., Nkurunziza, P., Anajemba, J. H., Bashir, A. K..  2018.  On Detection of Sybil Attack in Large-Scale VANETs Using Spider-Monkey Technique. IEEE Access. 6:47258–47267.
Sybil security threat in vehicular ad hoc networks (VANETs) has attracted much attention in recent times. The attacker introduces malicious nodes with multiple identities. As the roadside unit fails to synchronize its clock with legitimate vehicles, unintended vehicles are identified, and therefore erroneous messages will be sent to them. This paper proposes a novel biologically inspired spider-monkey time synchronization technique for large-scale VANETs to boost packet delivery time synchronization at minimized energy consumption. The proposed technique is based on the metaheuristic stimulated framework approach by the natural spider-monkey behavior. An artificial spider-monkey technique is used to examine the Sybil attacking strategies on VANETs to predict the number of vehicular collisions in a densely deployed challenge zone. Furthermore, this paper proposes the pseudocode algorithm randomly distributed for energy-efficient time synchronization in two-way packet delivery scenarios to evaluate the clock offset and the propagation delay in transmitting the packet beacon message to destination vehicles correctly. The performances of the proposed technique are compared with existing protocols. It performs better over long transmission distances for the detection of Sybil in dynamic VANETs' system in terms of measurement precision, intrusion detection rate, and energy efficiency.
Khalil, M., Azer, M. A..  2018.  Sybil attack prevention through identity symmetric scheme in vehicular ad-hoc networks. 2018 Wireless Days (WD). :184–186.

Vehicular Ad-hoc Networks (VANETs) are a subset of Mobile Ad-hoc Networks (MANETs). They are deployed to introduce the ability of inter-communication among vehicles in order to guarantee safety and provide services for people while driving. VANETs are exposed to many types of attacks like denial of service, spoofing, ID disclosure and Sybil attacks. In this paper, a novel lightweight approach for preventing Sybil attack in VANETs is proposed. The presented protocol scheme uses symmetric key encryption and authentication between Road Side Units (RSUs) and vehicles on the road so that no malicious vehicle could gain more than one identity inside the network. This protocol does not need managers for Road Side Units (RSUs) or Certification Authority (CA) and uses minimum amount of messages exchanged with RSU making the scheme efficient and effective.

Deeksha, Kumar, A., Bansal, M..  2017.  A review on VANET security attacks and their countermeasure. 2017 4th International Conference on Signal Processing, Computing and Control (ISPCC). :580–585.

In the development of smart cities across the world VANET plays a vital role for optimized route between source and destination. The VANETs is based on infra-structure less network. It facilitates vehicles to give information about safety through vehicle to vehicle communication (V2V) or vehicle to infrastructure communication (V2I). In VANETs wireless communication between vehicles so attackers violate authenticity, confidentiality and privacy properties which further effect security. The VANET technology is encircled with security challenges these days. This paper presents overview on VANETs architecture, a related survey on VANET with major concern of the security issues. Further, prevention measures of those issues, and comparative analysis is done. From the survey, found out that encryption and authentication plays an important role in VANETS also some research direction defined for future work.

Lim, K., Tuladhar, K. M., Wang, X., Liu, W..  2017.  A scalable and secure key distribution scheme for group signature based authentication in VANET. 2017 IEEE 8th Annual Ubiquitous Computing, Electronics and Mobile Communication Conference (UEMCON). :478–483.

Security issues in vehicular communication have become a huge concern to safeguard increasing applications. A group signature is one of the popular authentication approaches for VANETs (Vehicular ad hoc networks) which can be implemented to secure the vehicular communication. However, securely distributing group keys to fast-moving vehicular nodes is still a challenging problem. In this paper, we propose an efficient key management protocol for group signature based authentication, where a group is extended to a domain with multiple road side units. Our scheme not only provides a secure way to deliver group keys to vehicular nodes, but also ensures security features. The experiment results show that our key distribution scheme is a scalable, efficient and secure solution to vehicular networking.

Zhou, Lu, Liu, Qiao, Wang, Yong, Li, Hui.  2017.  Secure Group Information Exchange Scheme for Vehicular Ad Hoc Networks. Personal Ubiquitous Comput.. 21:903–910.

In this paper, a novel secure information exchange scheme has been proposed for MIMO vehicular ad hoc networks (VANETs) through physical layer approach. In the scheme, a group of On Board Units (OBUs) exchange information with help of one Road Side Unit (RSU). By utilizing the key signal processing technique, i.e., Direction Rotation Alignment technique, the information to be exchanged of the two neighbor OBUs are aligned into a same direction to form summed signal at RSU or external eavesdroppers. With such summed signal, the RSU or the eavesdropper cannot recover the individual information from the OBUs. By regulating the transmission rate for each OBU, the information theoretic security could be achieved. The secrecy sum-rates of the proposed scheme are analyzed following the scheme. Finally, the numerical results are conducted to demonstrate the theoretical analysis.

Tangade, S., Manvi, S. S..  2016.  Scalable and privacy-preserving authentication protocol for secure vehicular communications. 2016 IEEE International Conference on Advanced Networks and Telecommunications Systems (ANTS). :1–6.

Most of the existing authentication protocols are based on either asymmetric cryptography like public-key infrastructure (PKI) or symmetric cryptography. The PKI-based authentication protocols are strongly recommended for solving security issues in VANETs. However, they have following shortcomings: (1) lengthy certificates lead to transmission and computation overheads, and (2) lack of privacy-preservation due to revealing of vehicle identity, communicated in broadcasting safety-message. Symmetric cryptography based protocols are faster because of a single secret key and simplicity; however, it does not ensure non-repudiation. In this paper, we present an Efficient, Scalable and Privacy-preserving Authentication (ESPA) protocol for secure vehicular ad hoc networks (VANETs). The protocol employs hybrid cryptography. In ESPA, the asymmetric PKI based pre-authentication and the symmetric hash message authentication code (HMAC) based authentication are adopted during vehicle to infrastructure (V2I) and vehicle to vehicle (V2V) communications, respectively. Extensive simulations are conducted to validate proposed ESPA protocol and compared with the existing work based on PKI and HMAC. The performance analysis showed that ESPA is more efficient, scalable and privacy-preserving secured protocol than the existing work.

Grover, Kanika, Lim, Alvin.  2016.  Performance Comparison Between Broadcast Authentication Methods for Vehicular Networks. Proceedings of the 4th International Conference on Information and Network Security. :39–44.

For authenticating time critical broadcast messages, IEEE 1609.2 security standard for Vehicular Ad hoc Networks (VANETs) suggests the use of secure Elliptic Curve Digital Signature Algorithm (ECDSA). Since ECDSA has an expensive verification in terms of time, most commonly suggested alternate algorithms are TESLA and signature amortization. Unfortunately, these algorithms lack immediate authentication and non-repudiation. Therefore, we introduce a probabilistic verification scheme for an ECDSA-based authentication protocol. Using ns2 simulation tools, we compare the performance of all above-mentioned broadcast authentication algorithms. The results show with our proposed scheme, there is an increase in packet processed ratio over that of all the other algorithms.

Jia-Lun Tsai.  2014.  An Improved Cross-Layer Privacy-Preserving Authentication in WAVE-Enabled VANETs. Communications Letters, IEEE. 18:1931-1934.

In 2013, Biswas and Misic proposed a new privacy-preserving authentication scheme for WAVE-based vehicular ad hoc networks (VANETs), claiming that they used a variant of the Elliptic Curve Digital Signature Algorithm (ECDSA). However, our study has discovered that the authentication scheme proposed by them is vulnerable to a private key reveal attack. Any malicious receiving vehicle who receives a valid signature from a legal signing vehicle can gain access to the signing vehicle private key from the learned valid signature. Hence, the authentication scheme proposed by Biswas and Misic is insecure. We thus propose an improved version to overcome this weakness. The proposed improved scheme also supports identity revocation and trace. Based on this security property, the CA and a receiving entity (RSU or OBU) can check whether a received signature has been generated by a revoked vehicle. Security analysis is also conducted to evaluate the security strength of the proposed authentication scheme.