A Privacy-Preserving Medical Data Sharing Scheme Based on Consortium Blockchain

Electronic medical records (EMRs) can provide medical institutes with a number of research materials, which could promote the development of medical field. In order to protect patients' privacy while achieving efficient medical data sharing, we propose a privacy-preserving medical data sharing scheme based on consortium blockchain. In the scheme, a conditional anonymous tracing mechanism is designed to protect users' privacy, in which malicious users can be tracked when illegal behavior occurs. However, as the number of users grows, masses of medical data might touch the storage bottleneck of blockchain. Therefore, an on-chain-off-chain storage model is designed to alleviate the storage burden of blockchain, in which only the metadata of EMRs are recorded in blockchain while the patients' EMRs are stored in cloud after being encrypted. In order to resist the collusion attack, an improved proxy re-encryption scheme is introduced to ensure that EMRs can only be accessed by the authorized data requester. Moreover, security analysis and simulation demonstrate that the proposed scheme is more secure and efficient.