Privacy-aware attribute-based PHR sharing with user accountability in cloud computing

As an emerging patient-centric model of health information exchange, personal health record (PHR) is often outsourced to be stored at a third party. The value of PHR data is its long-term cumulative record relevant with personal health which can be significant in the future when faced with disease occurrences. As a promising public key primitive, attribute-based encryption (ABE) has been used to design PHR sharing systems. However, the existing solutions fail to achieve several important security objectives, that is, no need for a single authority to issue private keys to all PHR users, user access privacy protection, and user accountability. In this paper, we propose a multi-authority ciphertext-policy ABE scheme with user accountability and apply it to design an attribute-based PHR sharing system. In the proposed solution, the access policy is hidden and hence user access privacy is protected. In particular, the global identity of a misbehaving PHR user who leaked the decryption key to other unauthorized users can be traced, and thus the trust assumptions on both the authorities and the PHR users are reduced. Extensive analysis shows that the proposed scheme is provably secure and efficient.