Redactable Blockchain-Enabled Hierarchical Access Control Framework for Data Sharing in Electronic Medical Records

The application of blockchain to data sharing in an untrusted environment has received widespread industry attention in recent years. However, the tamper-proof property of blockchain brings protection for sharing data and also leads to a new limitation for the deletion of malicious data. Nowadays, many methods based on redactable blockchain with a chameleon hash is proposed to attempt to solve the above problem, but loss of effective access control to the modifiers can easily lead to breaking the positive characteristics of the blockchain. To address the aforementioned problem, a hierarchical access control redactable blockchain model for data sharing through attribute-based encryption and a chameleon hash is introduced. Under this model, the data owner can specify who can modify their data by setting an access policy and authenticating the modifier with a digital signature. The data owner's full control over rights is guaranteed, while the modifier's behavior is regulated. In addition, the hierarchical access control decentralized technique solves the overpowerful problem of center authority and single-point-of-failure problems in the existing works. The security analysis indicates that the proposed scheme achieves indistinguishable chosen plaintext attack security as well as collision resistance security. Performance analysis shows that the proposed scheme is more complete and has better efficiency compared with other schemes.