Abstract
Ciphertext-policy attribute-based encryption (CP-ABE) is a well-known cryptographic technology for guaranteeing data confidentiality but also fine-grained data access control. It enables data owners to define flexible access policy for cloud-based data sharing. However, the user revocation and attribute update problems existing in CP-ABE systems that are long-standing unsolved in the literature. In this paper, we propose the first access control (CP-ABE) scheme supporting user revocability and attribute update. Specifically, the user revocation is defined in the identity-based setting that does not conflict our attribute-based design. The cost brought by attribute update is efficient in the sense that we only concentrate on the update of the ciphertexts associated with the corresponding updated attribute. Moreover, the security analysis shows that the proposed scheme is secure under the decisional Bilinear Diffie-Hellman assumption.