Blockchain-Based Anonymous Authentication Mechanism with Semi-TTP for VANETs

With the rapid development of the vehicular ad hoc networks (VANETs), vehicle services are increasingly diversified. it will inevitably lead to authentication across data centers, privacy and security are crucial issues due to the unique characteristics of VANETs. The traditional cross-datacenter authentication mechanisms are mostly not anonymous or rely on a completely trusted third party (TTP) to guarantee the conditional anonymity of the user while TTP can easily obtain users' privacy. In this article, we introduce an lightweight anonymous authentication mechanism based on the combination of ring signature and blockchain technologies for VANETs. Our mechanism can achieve the following advantages: 1) achieving condition anonymity without TTP; 2) realizing a flexible anonymous authentication, in which a vehicle can decides whether to reauthentication or increases the intensity of anonymous according to the situation; 3)our mechanism is lightweight by recording signed pseudonym on blockchain to reduce the time consumption of anonymous authentication in different data centers, user only prove that pseudonym is recorded on the blockchain rather execute ring signature again; Our mechanism achieves these advantages by leveraging conditionally anonymous ring signature and extended blockchain technologies. These security features are demonstrated by carrying out security analysis. Meanwhile, extensive simulations are conducted to validate the efficiency and practicality of our mechanism.