An attribute based encryption scheme with fine-grained attribute revocation

As a new public key primitive, attribute-based encryption (ABE) is envisioned to be a promising tool for implementing fine-grained access control. When applying ABE schemes to practical applications, revocation mechanism is very necessary for any ABE schemes involving many users. Revocation for ABE schemes is a challenge issue since each attribute is conceivably shared by multiple users. Revocation of any single user would affect others who share his attributes. In this paper, we propose a KP-ABE scheme with fine-grained attribute revocation under the direct revocation model. In our scheme, we can revoke one attribute of a user instead of all attributes issued to him and the user can complete decryption as long as the unrevoked attributes of the user satisfy the access structure. The revocation does not affect any other user's private key. Moreover, our scheme supports an important property for achieving the user accountability to prevent illegal key sharing among colluding users. We show how to construct such a KP-ABE scheme with fine-grained attribute revocation and prove its security under the q-BDHE assumption in the standard model.