Blockchain-based Bidirectional Transformations for Access Control and Data Sharing in EMRs

Electronic medical records (EMRs) are scattered in different hospitals, which hinders the process of data sharing. On the other hand, people with different roles should access different parts of data, thus we need a way to control the accessibility. To address these issues, we propose a blockchain-based data sharing system that gathers EMRs into blockchain and controls data sharing through bidirectional transformation. In our system, EMRs are encoded with a carefully designed data structure that stores not only data, but also data's read/write permission for different roles. We redesigned a bidirectional transformation language based on our previous work BiGUL by taking access control into consideration, and the accessibility are checked during program execution in both direction to avoid un-authorized data access. Further more, each bidirectional transformation program and updates on the shared data are stored in the blockchain in a transaction-like form. The immutability of blockchain guarantees EMR's data integrity.