MedSharer: A Patient-Centric Architecture for Consent-Based Medical Data Exchange

Sharing medical data across clinicians and institutions is useful but risky, and patients rarely control who sees their records. We propose MedSharer, a patient-centric architecture in which the patient holds the data and grants revocable, time-limited, scope-limited consent to each clinician. Clinical content is exchanged as structured HL7 FHIR summaries, encrypted and stored off-chain. A blockchain is used only to record consent decisions and access events, never the data itself, which keeps the design compatible with the GDPR right to erasure. We describe the threat model, the architecture, the consent lifecycle and the regulatory considerations. We also report a research prototype of about 530 lines with 23 passing functional tests and micro-benchmarks: a complete access (request, key release and decryption of 20 resources) takes under 1 ms of CPU time at the median on a simulated ledger. The prototype runs in one process on synthetic data, so the results do not cover a real ledger, network, mobile devices or clinical use.