Fine-grained access control system based on fully outsourced attribute-based encryption

Attribute-based encryption (ABE) has potential to be applied in cloud computing applications to provide fine-grained access control over encrypted data. However, the computation cost of ABE is considerably expensive, because the pairing and exponentiation operations grow with the complexity of access formula. In this work, we propose a fully outsourced ciphertext-policy ABE scheme that for the first time achieves outsourced key generation, encryption and decryption simultaneously. In our scheme, heavy computations are outsourced to public cloud service providers, leaving no complex operations for the private key generator (PKG) and only one modular exponentiation for the sender or the receiver, and the communication cost of the PKG and users is optimized. Moreover, we give the security proof and implement our scheme in Charm, and the experimental results indicate that our scheme is efficient and practical.