FDR-ABE: Attribute-Based Encryption with Flexible and Direct Revocation

In attribute-based encryption (ABE) systems, the revocation issue is essential and difficult, since users may change their attributes frequently in practice and each attribute is conceivably shared by multiple users. To our knowledge, all the existing ABE schemes fail to support flexible and direct revocation due to the burdensome update of attribute secret keys and cipher texts. Aiming at tackling the challenge above, in this paper, we formalize the notion of cipher text policy ABE with flexible and direct revocation (FDR-CP-ABE), and give out a concrete construction, which supports direct attribute and user revocation and is applicable to the data sharing architecture. The proposed FDR-CP-ABE scheme outperforms the previous revocation-related methods in that it has constant-size cipher texts and only partial cipher texts need to be updated whenever revocation events occur. Furthermore, we show that our FDR-CP-ABE scheme is provably secure in the standard model and it cannot be achieved by trivial combinations of the techniques of CP-ABE and BE.