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Vehicle-to-everything (V2X) is the communication technology designed to support road safety for drivers and autonomous driving. The light-weight security solution is crucial to meet the real-time needs of on-board V2X applications. However, most of the recently proposed V2X security protocols—based on the Elliptic Curve Digital Signature Algorithm (ECDSA)—are not efficient enough to support fast processing and reduce the communication overhead between vehicles. ECDSA provides a high-security level at the cost of excessive communication and computation overhead, which motivates us to propose a light-weight message authentication and privacy preservation protocol for V2X communications. The proposed protocol achieves highly secure message authentication at a substantially lower cost by introducing a hash chain of secret keys for a Message Authentication Code (MAC). We implemented the proposed protocol using commercial V2X devices to prove its performance advantages over the standard and non-standard protocols. We constructed real V2X networks using commercial V2X devices that run our implemented protocol. Our extensive experiments with real networks demonstrate that the proposed protocol reduces the communication overhead by 6 times and computation overhead by more than 100 times compared with the IEEE1609.2 standard. Moreover, the proposed protocol reduces the communication overhead by 4 times and the computation overhead by up to 100 times compared with a non-standard security protocol, TESLA. The proposed protocol substantially reduces the average end-to-end delay to 2.5 ms, which is a 24- and 28-fold reduction, respectively, compared with the IEEE1609 and TESLA protocols.

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In support of traffic safety applications, vehicular networks should offer a robust Medium Access Control (MAC) layer protocol that can provide a reliable delivery service to safety-related messages. As the safety applications generally use broadcasting to propagate their messages, a reliable broadcast protocol is essential. In general, however, broadcast is considered as unreliable by nature in contrast to unicast. This paper introduces a novel MAC protocol, called a Hybrid Cooperative MAC (HCMAC), which can substantially enhance the reliability of broadcast in vehicular networks by employing a notion of channelization. HCMAC introduces a hybrid protocol that combines a time slot allocation of Time Division Multiple Access (TDMA) and a random-access technique of Carrier Sense Multiple Access (CSMA) and thus minimizes the probability of data collisions. In addition, its feedback strategy further enhances the system performance by preventing transmissions during time slots that experience collisions. Through analysis and simulations, we compare the performance of HCMAC with VeMAC, an existing TDMA protocol. The results demonstrate that HCMAC can offer substantially faster channel access and lower collision rate compared with VeMAC.

Time synchronization is an essential issue in industrial wireless sensor networks (IWSNs). It assists perfect coordinated communications among the sensor nodes to preserve battery power. Generally, time synchronization in IWSNs has two major aspects of energy consumption and accuracy. In the literature, the energy consumption has not received much attention in contrast to the accuracy. In this paper, focusing on the energy consumption aspect, we introduce an energy-efficient reference node selection (EERS) algorithm for time synchronization in IWSNs. It selects and schedules a minimal sequence of connected reference nodes that are responsible for spreading timing messages. EERS achieves energy consumption synchronization by reducing the number of transmitted messages among the sensor nodes. To evaluate the performance of EERS, we conducted extensive experiments with Arduino Nano RF sensors and revealed that EERS achieves considerably fewer messages than previous techniques, robust time synchronization (R-Sync), fast scheduling and accurate drift compensation for time synchronization (FADS), and low power scheduling for time synchronization protocols (LPSS). In addition, simulation results for a large sensor network of 450 nodes demonstrate that EERS reduces the whole number of transmitted messages by 52%, 30%, and 13% compared to R-Sync, FADS, and LPSS, respectively.

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The deployment of vehicular networks is considered crucial for traffic safety of future vehicles. Thus, researchers are making extensive efforts to improve the performance of the IEEE802.11p standard. Many researchers have proposed various MAC protocols to mitigate the chronicle problems of the IEEE802.11p -for example, the unreliable transmission of safety-related messages. However, most of the previous evaluations of the reliability problem have been done either via mathematical analysis or simulations. In this paper, we conducted actual experiments and analyzed the performance of two MAC protocols: IEEE802.11p and HCMAC, a hybrid MAC protocol recently reported. Using commercial V2X devices, we measured the performance in terms of received signal strength indicator (RSSI), packet delivery ratio (PDR), and packet inter-reception time (PIR). We tested the connectivity performance under various mobility scenarios. In addition, this paper investigates the impact of collisions on the overall performance. For a range of collision levels, an extensive set of experiments demonstrate that HCMAC outperforms the MAC of IEEE802.11p in terms of PDR and PIR up to 88% and 47%, respectively. INDEX TERMS VANET, IEEE802.11p, HCMAC, Cohda wireless, field testing. 1 DSRC standard defines such a beacon message as a Basic Safety Message (BSM). Hereafter, the terms ''beacon'' and ''BSM'' are interchangeably used.

Recently many security protocols have been proposed for road safety applications in Vehicleto-everything (V2X) communications. Most of them, however, do not fully satisfy the requirements of light-weight and fast processing, which are special properties for V2X. Most of the previous authentication protocols assume that a Certificate Authority (CA) is present within the communication range from all the vehicles, which is not practical for moving vehicles. We propose a light-weight security protocol for authentication and privacy protection for V2X. It employs two security hardware devices, Biometric Device (BD) and Tamper Proof Device (TPD), which verifies the driver and securely keeps the keys, respectively. It decentralizes the CA's tasks by locally generating pseudo-identity and private keys to preserve privacy and provide authentication in Vehicle-to-Vehicle (V2V) communication. In addition, we propose an authentication signature protocol using a notion of hash-chain key generation. We implemented the proposed key generation and authentication protocol using NS-3 simulator. Our extensive simulations demonstrated that the proposed authentication protocol significantly enhances the security level while protecting the conditional privacy of vehicles by utilizing anonymous identities. The proposed protocol has a 20% ∼ 85% less communication overhead compared with the previous protocols.INDEX TERMS Hash-chain, MAC algorithm, privacy, two-factor authentication, biometric, tamperproof.