FXChain: A Multi-consortium Permissioned Blockchain with Flexible Privacy-Preserving Strategies

Permissioned blockchain is often used in multi-consortium applications due to its unique features such as provenance, immutability, and tamper-resistance. For these applications working in a malicious environment, privacy protection is very important. There have been many works attempting to solve the challenge of privacy protection. However, existing works suffer from problems such as low flexibility, difficulty in regulation and waste of computation resources. To address these problems, we propose FXChain, a multi-consortium permissioned blockchain system with a flexible privacy-preserving strategy. We provide a general cross-ledger transaction framework to support and help designing the strategy. In this framework, we divide the cross-ledger transaction into two steps, provide more flexibility to users. We classify privacy requirements into multiple levels from the strongest to the weakest in detail, and design a flexible privacy-preserving strategy for cross-ledger transactions, allowing users to choose proper privacy scheme according to their own demands. We conduct experiments to evaluate the overhead of each level and the overall performance of the system, helping users making better choices. The experiments also show that the impact of our privacy protection scheme is acceptable.