BTMDS: : Blockchain trusted medical data sharing scheme with privacy protection and access control

With the development of smart healthcare, eliminating information silos through trusted data sharing has become a social consensus, but there are still many problems that need to be solved. The multi-party sharing process of medical data usually occurs in an untrusted network environment, and the separation of data ownership and usage rights can result in the leakage of patients’ private information. Meanwhile, the communication and computation overheads of existing medical data sharing schemes are too large, resulting in inefficient data sharing. To address the above problems, we propose a blockchain-based trusted medical data sharing scheme (BTMDS) with privacy protection and access control. In it, we subdivided patient privacy into identity and data privacy, and designed a privacy protection mechanism for blockchain medical data sharing using local differential privacy technology and searchable encryption technology. The cloud server acts as a proxy server, and the on-chain-off-chain storage structure of the blockchain and the cloud server implements fine-grained access control to prevent conspiracy attacks. Security analysis proves the security of BTMDS and prioritizes it over other schemes. In terms of performance, BTMDS saves 30% and 48% in the decryption phase compared to Feng and Chen schemes, which is more suitable for digital healthcare data sharing services.