Implementation of Hyperledger Besu Permissioned Blockchain for Electronic Health Record Integrity Verification Using off-Chain AES-256 Encryption and SHA-256 Cryptographic Hashing

Digital transformation in healthcare facilities requires robust data security to protect Electronic Health Records (EHR) against internal data tampering and unauthorized breaches. This paper presents RS MedChain, a dual-layer architecture combining off-chain MySQL database management with permissioned blockchain verification deployed on Hyperledger Besu using the QBFT consensus algorithm. Patient clinical attributes are encrypted off-chain using AES-256-CBC with patient-derived secret keys, while 32-byte SHA-256 cryptographic hashes are anchored onto the MedicalRecord.sol smart contract via JSON-RPC. Experimental evaluations demonstrate a 98.65% reduction in EVM execution gas overhead (44,210 gas per record) compared to on-chain text storage. The system achieves a peak throughput of 450 TPS with 1.02-second block finality, detecting 100% of data tampering scenarios across a six-layer verification pipeline. RS MedChain proves scalable and fully compliant with health privacy regulations.