Authenticated Key Release for Electronic Health Records During Migration to Post-Quantum Cryptography

Migration to post-quantum cryptography must preserve the conditions for releasing electronic health record keys. This study evaluates a signed off-chain release protocol binding a trusted accepted event to the expected recipient and record, migration policy, and paired single-use state. It supports RSA, ML-KEM-only, and a custom dual-contribution hybrid. The inherited zero-knowledge proof does not bind requester and record identities; accepted events remain trusted inputs. Symbolic agreement holds for an external adversary and one honest recipient. Implementation tests exercise real cryptographic operations, rejection, and failure cases; 27 coordinated races between distinct releases for one grant each returned exactly one key. Issuer-side exposure records support an optional inventory gate conditional on truthful histories and consistent record-key identity; content-identifier alias tests reveal the limits of per-identifier exposure histories. Across five restarted native processes, validated preloading reduced median legacy and hybrid service latencies from 48.501 to 2.085 ms and from 48.824 to 2.404 ms relative to per-call RSA import; ML-KEM-only remained near 1.5 ms. These operational comparisons use unmatched security levels and exclude network, blockchain, concurrent-load, and durable-state costs. Static recipient keys provide no forward secrecy, and later post-quantum protection cannot repair earlier key exposure.