Vehicular Ad Hoc Networks (VANETs) can provide participants with security services and entertain-ment information during the driving. To guarantee correct and smooth operations of VANETs, it is necessary to achieve efficient authentication with user privacy preserving. Current solutions either cannot satisfy privacy requirements, or are not efficient in message verification. Moreover, all the existing schemes are RSU-based. We, for the first time, apply VANETs to emergency communication during disaster rescue, and effective authentication scheme is proposed in accordance with the actual environment, where there is no fixed road-side unit (RSU). In this paper, we present an efficient identity based signature scheme EPAS, which satisfies conditional privacy requirements through software solution. In aspect of efficiency, both lightweight signature and batch verification are employed to provide effective authentication. Extensive theoretical and experimental analyses demonstrate the security and efficiency of EPAS in terms of privacy-preserving and low authentication delay.

The existing communication schemes are often unusable in natural disasters and public emergencies. But requirements of information collection and data transmission in emergency scenario are very imperative. Thus, sensor networks ad hoc networks are required in the emergency communication systems. For example, rescue vehicles equipped with wireless communication devices, sensors, and cameras are regularly used to collect and transmit the real-time information for the rescue action. The paper focuses on security solutions for the vehicular ad hoc networks (VANETs) in the emergency communication cases, in which the communication infrastructures are not always available. An expedite privacy-preserving emergency communication (EPEC) scheme is presented for the vehicles to securely connect with the others in the neighbor area even when the trusted infrastructures are destroyed by the disaster. EPEC satisfies conditional privacy preservation requirements, in which both lightweight signature and batch verification are employed to provide efficiency. We also show the proof of the security, feasibility, and efficiency of our EPEC by the theoretical and experimental analyses.

In a traditional electronic auction, the centralized auctioneer and decentralized bidders are in an asymmetric structure, where the auctioneer has more ability to decide the auction result. This asymmetric auction structure is not fair to the participants and not suitable for data auctions in the Internet of Things (IoT). The blockchain-based auction system, with participant equality and fairness, is typically symmetrical and particularly suitable for IoT data sharing. However, when applied to IoT data sharing in reality, it faces privacy and efficiency problems. In this context, how to guarantee privacy and break the inherent performance bottleneck of blockchain is still a major challenge. In this paper, a consensus-based distributed auction scheme is proposed for data sharing, which enforces privacy preservation and collusion resistance. A reverse auction-based decentralized data trading model is introduced to solve the trust problem without a centralized auctioneer, where bidders reach consensus on the auction result. Specifically, we devise a differentially private auction mechanism to incentivize data owners to participate in data sharing. An effective hybrid consensus algorithm is constructed among bidders to reach consensus on the auction result with improved security and efficiency. Theoretical analysis shows that the proposed scheme ensures the properties of privacy preservation, incentive compatibility and collusion resistance. Experimental results reveal that the proposed mechanism guarantees the data sharing efficiency and has certain scalability.

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