Abstract: The digital currency, represented by Bitcoin, was designed to be a decentralized system. And this property makes the regulation more difficult. However, the research of designing a regulatable digital currency is very limited. In this paper, we introduce a new digital currency model based on two chains scheme, public blockchain and consortium blockchain. As the core participant, the consortium blockchain collects and confirms every transaction, determines the status of the system, and stores the complete transaction records. The users’ private information is guaranteed by the secret sharing in the consortium blockchain and also can be decrypted by the voting committee. Based on the characteristics and requirements of the consortium blockchain, we also introduce an agreement protocol based on the Credit Practical Byzantine Fault Tolerance and use the simplified agreement protocol to offer high throughput for our model and flexibility of the system. With the view-change and checkpoint protocol, we can dynamically adjust the nodes’ status and authority. Extensive analysis and experimental results indicate that our proposed method is both efficient and secure. We believe that this is the first work that has the capacity of the tamper-resistant, traceability, decentralize and regulation.

Key words: block chain, consortium chain, regulation, digital currency, agreement