MAVP-FE: Multi-authority vector policy functional encryption with efficient encryption and decryption

In cloud, data access control is a crucial way to ensure data security. Functional encryption (FE) is a novel cryptographic primitive supporting fine-grained access control of encrypted data in cloud. In FE, every ciphertext is specified with an access policy, a decryptor can access the data if and only if his secret key matches with the access policy. However, the FE cannot be directly applied to construct access control scheme due to the exposure of the access policy which may contain sensitive information. In this paper, we deal with the policy privacy issue and present a mechanism named multi-authority vector policy (MAVP) which provides hidden and expressive access policy for FE. Firstly, each access policy is encoded as a matrix and decryptors can only obtain the matched result from the matrix in MAVP. Then, we design a novel function encryption scheme based on the multi-authority spatial policy (MAVPFE), which can support privacy-preserving yet non-monotone access policy. Moreover, we greatly improve the efficiency of encryption and decryption in MAVP-FE by shifting the major computation of clients to the outsourced server. Finally, the security and performance analysis show that our MAVP-FE is secure and efficient in practice.