Enabling Privacy-Preserving External Sharing of Electronic Medical Records Through a Tripartite Hybrid Blockchain Architecture
Abstract
Patient-centric privacy, rapid interoperability, and verifiable auditability remain open problems in smart-healthcare data exchange. We present a tripartite hybrid blockchain framework that splits electronic medical records (EMRs) across three permissioned ledgers-Patient Chain, Provider Chain, and Social Chain-to decouple clinical processing from privacy-preserving external sharing. A crosschain Boneh-Lynn-Shacham aggregate-signature scheme fuses dual-chain approvals into a single 32byte proof, reducing signature storage by and enabling constant-time verification. Zeroknowledge redaction releases only Tier-2 statistical summaries through the Social Chain, embedding GDPR/HIPAA principles of data minimization, purpose limitation, and complete auditability into the protocol rather than post-hoc governance. Security reductions to the Computational Diffie-Hellman problem and gambler's-ruin analysis show that, at adversarial hash power, safe external finality requires 118 confirmations, which is fewer than dual- or single-chain baselines. A three-chain prototype on private Ethereum sustains < 6 s mean latency at , while ZK processing averages 288.3 ms per request. The framework therefore delivers stronger security, lower cost, and regulatorready compliance, offering a practical blueprint for privacy-preserving EMR sharing in nextgeneration healthcare networks.
Keywords
blockchain, electronic medical records, cross-chain signatures, BLS aggregation
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