A Revocable Outsourcing Attribute-Based Encryption Scheme

Attribute-Based Encryption (ABE) is a generalized cryptographic primitive from normal public key encryption. It provides an access control mechanism over encrypted message using access policies and ascribed attributes. This scheme can solve the privacy issue when data is outsourced to cloud for storage well. However, there are some practical issues which must be fixed before ABE becomes applicable. One is that both the ciphertext size and the decryption time grows with the complexity of the access policy, which brings pressure to mobile devies. The other is that, from practical point of view, some users might be disabled for some attributes or be removed from the system. It demands on flexible revocation mechanism supporting both user and attribute granularities. In this research, we propose a solution adopting techniques on secure outsourcing of pairings to support outsourcing computation and adopting some techniques based on the tree-based scheme to solve user revocation and attribute revocation. We also give its security model and proof.