P$^{2}$ESchain: Patients-Controlled and Privacy-Preserving EHRs Sharing Based on Blockchain

Abstract

The widespread application of Ehealth systems and medical cloud services has had a profound impact on human society. However, centralized electronic health systems have serious security and privacy risks. In addition, because electronic health records (EHRs) rely on centralized or semi-trusted medical cloud storage platforms, patients lose control over their own health data. Fortunately, the integration of blockchain technology can effectively address these issues. But the transparent on-chain data storage may lead to the leakage of sensitive information in EHRs. To mitigate these vulnerabilities, we intoduce a patient-centric privacy-preserving electronic health record sharing scheme based on blockchain-cloud collaboration (P$^{2}$ESchain). In this scheme, encrypted electronic health records are stored in a semi-trusted medical cloud, and the corresponding hash values are recorded on the blockchain. To realize a secure patient-autonomous sharing mechanism, we construct an anonymous authentication scheme to achieve privacy-protected access right delivery through the blockchain. We also design a secure EHR authorization and delegation algorithm based on Revocable Identity-Based Broadcast Proxy Re-Encryption (RIB-BPRE), ensuring that patients can still receive timely treatment when they are unconscious. The security of the scheme is verified through formal security analysis, and it has been deployed on the local chain (Geth) and the Goerli testnet. Evaluation results show that P$^{2}$ESchain has both security and efficiency, and is suitable for EHRs sharing scenarios in cloud environments.