MedChain: A Privacy-Preserving Framework for Scalable Electronic Health Record Sharing on Blockchain and InterPlanetary File System

The secure and scalable sharing of electronic health records (EHRs) remains a fundamental challenge in modern health-care systems due to conflicting requirements of privacy, regulatory compliance (HIPAA, GDPR), and real-time clinical access. Existing blockchain-based solutions suffer from three critical limitations, including static access control policies that cannot adapt to emergency scenarios, complete transparency of policy evaluation leading to attribute leakage, and linear degradation of throughput with policy complexity. The proposed MedChain, a framework introducing four novel contributions: Dynamic Attribute-Based Proxy Re-Encryption (DAB-PRE) enabling time-bound and emergency breakout access without re-encrypting underlying data; Zero-Knowledge Policy Verification (ZK-PV) allowing smart contracts to validate access requests without revealing sensitive attribute values; Adaptive EHR Sharding that dynamically adjusts IPFS shard sizes based on access frequency, reducing cold-start latency by 64%; and Layered Revocation Cascade providing granular revocation at patient, provider, and record-type levels within 2.3 seconds. Using the MIMIC-III benchmark (46,520 patients, 100,000 access traces), we demonstrate: 99.4% storage reduction vs. pure blockchain, 0.95s median latency (43% improve-ment over prior work), 2,450 requests/second throughput with 150 IPFS nodes, and provable security under the q-DBDH assumption. Comprehensive comparisons with MedRec, FHIRChain, Ancile, and PriHac confirm MedChain’s superiority across all metrics.

@article{Venkateswaran2026,
  title     = {MedChain: A Privacy-Preserving Framework for Scalable Electronic Health Record Sharing on Blockchain and InterPlanetary File System},
  journal   = {International Journal of Advanced Computer Science and Applications},
  volume    = {17},
  number    = {6},
  year      = {2026},
  publisher = {The Science and Information Organization},
  author    = {S. Venkateswaran and N. Vijayaraj},
  doi       = {10.14569/IJACSA.2026.0170652},
  url       = {https://doi.org/10.14569/IJACSA.2026.0170652}
}