Fine-grained data sharing in cloud computing for mobile devices

Due to the convenience, the data sharing in cloud computing via mobile devices has become more and more popular. However, data confidentiality and online computational cost still present practical concerns to the deployment of data sharing in cloud computing for mobile devices. Existing data sharing protocols in cloud computing either cannot support the flexible sharing style for the encrypted data, or suffer from massive online computational cost that scales with the complexity of the access policy. In this paper, to cope with these challenging concerns, we propose a new data sharing protocol for cloud computing by using a new cryptographic primitive named online/offline attribute-based proxy re-encryption and the transform key technique. To the best of our knowledge, the proposed data sharing protocol is the first one featuring with fine-grained access control, flexible sharing, data confidentiality, and minimum online computational cost on the user side at the same time. Furthermore, the proposed online/offline attribute-based proxy re-encryption scheme may be of independent interest. At last, extensive analysis shows that our proposed data sharing protocol is secure in terms of data confidentiality, and suitable for mobile devices in terms of online computational cost.