A pairing-free proxy re-encryption scheme suitable for cloud medical information systems

The cloud medical information system provides a platform for patients and doctors to share data. Patients send files containing personal medical data to cloud storage, which can reduce their own storage burden and facilitate other doctors’ access to data files. To ensure the privacy of sensitive information deposited in the communal network platform, patients should encrypt their data before submitting it to the network platform. Nevertheless, the effective sharing of encrypted data in the public cloud brings us new challenges. Proxy re-encryption (PRE) supports a proxy, who is unable to decrypt the original ciphertext, converts the original ciphertext to a new ciphertext using the re-encryption key, and the new receiver can decrypt the new ciphertext to obtain plaintext. In this article, we design a new PRE programme for cloud medical information systems. There are two merits in the new scheme. To begin with, it is indistinguishable against chosen-ciphertext attacks secure and is resistant to collusion attacks, which means that the proxy is incompetent to acquire data owner’s secret key even if he colludes with data receiver. Secondly, it has higher computational efficiency compared to other schemes because it does not use bilinear pairing operations.