A blockchain-based privacy-preserving transaction scheme with public verification and reliable audit

With the continuous development of Internet of Things, finance, big data and many other fields, blockchain has been widely used in these areas for transactions, data sharing, product traceability and so on. Numerous assets have appeared in the blockchain, and there are some levels of conflicts among privacy protection of these assets, transaction transparency and auditability in blockchain; so how to provide privacy preserving, make public verifications and audit the encrypted assets are challenging problems. In this paper, we propose a privacy-preserving transaction scheme with public verification and reliable audit in blockchain. First, we provide privacy preserving of transaction contents based on homomorphic encryption. It is flexible, as we decouple user identity and transaction contents. Then, we propose and design a multiplicative zero-knowledge proof with formal security analysis. Furthermore, several verification rules are defined by us in the scheme, such as balance verification and multiplicative verification based on the proposed multiplicative zero-knowledge proof. Our scheme enables reliable and offline auditing for each transaction, and we aggregate the zero-knowledge proofs to save the ledger space. Finally, we make a security analysis of our proposal in terms of transaction confidentiality, public verification and audit reliability, and we give a performance analysis of the proposed scheme.