A Certificateless Provable Data Possession Scheme for Cloud-Based EHRs

Electronic health records (EHRs: digital collections of patient health status and diagnosis) are generally shared, analyzed and stored on cloud servers. One operational challenge is to ensure that EHRs are stored correctly, for example using provable data possession (PDP). Seeking to contribute to the literature, we propose a certificateless PDP scheme for cloud-based EHRs. In our scheme, we distribute multiple copies of EHRs on different cloud servers to allow for corrupted EHRs to be recoverable from other intact copies. The scheme is also designed to resist copy-summation attack which assures that cloud servers are storing EHRs honestly. In our approach, EHRs are stored in ciphertext form so that only authorized users can decrypt and gain access to the information. We also design a new data structure – map version marker table (MVMT) – for block-level dynamic operations and data traceability. Specifically, MVMT allows an authorized doctor to access historical EHRs to inform their diagnosis and decision-making. The security and performance analyses show that our scheme is secure (assuming the intractability of the computational Diffie-Hellman problem) and is practical to support cloud-based EHR applications.