BUA: A Blockchain-based Unlinkable Authentication in VANETs

Authentication with unlinkability is one of the critical requirements for the security of VANETs. Unlinkability prevents attackers from linking multiple messages to infer vehicular privacy. Pseudonymous authentication schemes are widely adopted to achieve unlinkable authentication. However, they need multiple interactions with a trusted third-party to update pseudonym as well as the attached information. In order to address this issue and provide effective services in distributed systems, we propose a blockchain-based unlinkable authentication protocol called BUA, where Service Manager (SM) of each domain acts as the nodes of consortium blockchain to construct a distributed system. Each SM covers a certain logical area and maintains a sequence of consistent blocks, which hold vehicular registration data. Based on the system, vehicles use homomorphic encryption to self-generate any number of pseudonyms to achieve unlinkability. Pseudonymous validity and ownership can be verified locally by each SM. Performance evaluation results of the proposed scheme show that our protocol provides stronger security with less computation and communication overhead.