Toward Efficient and Reliable Private Set Computation in Decentralized Storage

Abstract

Decentralized storage is recognized as a promising blockchain application for building trustworthy data-sharing services. Recently, privacy-preserving decentralized storage has attracted tremendous attention from the research community, due to the inherent transparent access properties of blockchain. That is, multi-users can search over encrypted data from multi-owners via untrusted storage servers. Private Set Intersection (PSI) is regarded as an ideal cryptographic scheme for this scenario because it allows multiple parties to collaboratively execute private set computations without revealing additional information. However, existing solutions do not consider the necessary verification and fault tolerance of PSI results, which is the indispensable security requirements in decentralized storage. To fill the gap, in this work, we introduce the first reliable PSI scheme for decentralized storage that provides results verifiability and fault tolerance for private set operations. Our design leverages authenticated indexing structures and Shamir's secret sharing algorithm for constructing our reliable PSI scheme with fault tolerance. To address the potential malicious behaviors of dishonest users or servers, we also propose a blockchain-assisted arbitration protocol that enables public arbitration in a privacy-preserving manner. We rigorously provide security analysis and complete the prototype implementation on Fabric. Extensive results demonstrate its practicability and feasibility for existing decentralized storage.