The vehicular ad-hoc networks (VANETs) is one of the most promising application in the communications of smart vehicles and the smart transportation systems. However, authentication and privacy of users are still two vital issues in VANETs. It is crucial to prevent internal vehicles from broadcasting the forged messages while preserving the privacy of vehicles against the tracking attack. Moreover, in the traditional mode, the transactional data storage provides no distributed and decentralized security, so that the third party initiates the dishonest behaviors possibly. In this paper, based on blockchain technique, we propose a traceable and decentralized the Internet of Vehicle system framework for communication among smart vehicles by employing of a secure access authentication scheme between vehicles and RoadSide Units (RSUs). On the one hand, this scheme allows that vehicles employ pseudonyms for Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communications anonymously in the non-fully trusted environment. On the other hand, the transparency of vehicles in authentication and announcement is preformed efficiently by the blockchain technology. In addition, the transaction information is tamperresistant that provides the distributed and decentralized property for the different cloud servers. With the help of Certificate Authority (CA) and the RoadSide Units (RSUs), our proposal achieves the conditional privacy to trace the real identity of the malicious vehicle in the anonymous announcements as well. Finally, through the theoretical analysis and simulations, our scheme is able to construct a secure and decentralized system framework of VANETs with accountability and privacy preservation.

As an important method of making democratic decisions, voting has always been a topic of social concern. Compared with the traditional, e-voting is widely used in various decision scenarios because of the convenience, easy to participate and low cost. However, the proposed e-voting protocols are at the risk of excessive authority and tampered information, which makes it impossible to achieve true fairness and transparency in e-voting. By combining the blockchain technology, it enables to solve these problems with the decentralization and tamper-resistant features. Moreover, the misoperations of the voters will also affect this fairness, such as voting for non-candidates, abstention or repeated voting. Therefore, to ensure the efficiency of the voting process and maintain the fairness of the voting environment, it is important to append the function of audit in e-voting protocol. This paper proposes an e-voting protocol based on blockchain, which provides transparency in the process of voting. At the same time, this scheme has the ability to audit voters operating incorrectly and resist quantum attacks by adopting the certificateless and code-based cryptography. After performance analysis, our scheme is suitable for the small-scale election and has some advantages in security and efficiency when the number of voters is small.