RPSC: Regulatable Privacy-Preserving Smart Contracts on Account-Based Blockchain

Smart contracts have been widely used to develop decentralized applications on account-based blockchain. The privacy issues of smart contracts have also received attention from researchers, and many privacy-preserving schemes and applications have been proposed. However, most existing schemes cannot achieve flexible conversion between private and public data. And the overly secure privacy-preserving scheme directly makes the regulation impossible. To mitigate these limitations, we propose a flexible privacy-preserving smart contracts with regulation (RPSC) system over the account-based blockchain. We first design a two-layer commitment structure that enables the fine-grained privacy protection (identity anonymity and data confidentiality) and flexible data state transitions. Then we combine a public-key encryption scheme with a zk-SNARKs scheme to achieve regulation property while keeping user's identity from others. Moreover, we prove that our scheme is secure, including privacy, soundness and traceability. Finally, we integrate RPSC into an account-based blockchain and implement two applications to evaluate the system performance. The evaluation results show our system performs effectively in practical settings.