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Multi-authority attribute-based access control scheme in mHealth cloud with unbounded attribute universe and decryption outsourcing

Multi-Authority Attribute-Based Encryption (MA-ABE) is a practical cryptographic primitive for enforcing fine-grained attribute-based access control of personal health information (PHI) in mobile healthcare (mHealth) cloud. Existing schemes are either limited to restricted attribute universe or lack of efficient decryption algorithm for users. In this paper, we propose an efficient and secure multi-authority attribute-based access control scheme for PHI in mHealth cloud. The proposed scheme simultaneously supports unbounded attribute universe and offers efficient decryption outsourcing approach without leaking the PHI privacy. It enables the PHI owner to define access policy in the form of any monotonic access structures. We prove the security in the standard model. Compared with relevant schemes, our scheme can reduce the user's decryption cost from increasing linearly with the number of attributes to constant.