MISC: Flexible Data Management for Private Smart Contract

Abstract

Private Smart Contracts (PSCs) aim to settle the privacy protection issue for sensitive data on the blockchain (a.k.a., on-chain data) while inheriting the computation functionality of general smart contracts. However, most of the existing PSCs focus on secure computation and ignore the secure and flexible management of on-chain data, making it difficult to support flexible user permission modes efficiently. Further, although a few on-chain data management schemes have been proposed to manage data on the blockchain, they provide insufficient support for scenarios where data must be managed concurrently by managers with different privilege levels. This paper proposesMISC, a novel solution that features efficient and flexible data management capabilities for managing on-chain data in private smart contracts.MISCleverages a novel Double Trapdoor Homomorphic Proxy Re-encryption (DT-HPRE) scheme and Trusted Execution Environments (TEEs) to ensure (1) low-overhead, flexible permission control over on-chain data and (2) a harmonious mechanism for both privileged and constrained managers. We prove the security ofMISCunder the Universal Composability (UC) framework to demonstrate its data confidentiality guarantees, user revocation, and computation integrity. Further, we implementMISC, and the performance evaluation shows that on-chain data access for one hundred data points is practically achieved in 5.8 s (under privileged managers) and 9.7 s (under constrained managers) using its off-chain design.