Attribute-based encryption (ABE) scheme is more and more widely used in the cloud storage, which can achieve fine-grained access control. However, it is an important challenge to solve dynamic user and attribute revocation in the original scheme. In order to solve this problem, this paper proposes a ciphertext-policy ABE (CP-ABE) scheme which can achieve attribute level user attribution. In this scheme, if some attribute is revoked, then the ciphertext corresponding to this attribute will be updated so that only the individuals whose attributes meet the access control policy and have not been revoked will be able to carry out the key updating and decrypt the ciphertext successfully. This scheme is proved selective-structure secure based on the q-Parallel Bilinear Diffie-Hellman Exponent (BDHE) assumption in the standard model. Finally, the performance analysis and experimental verification have been carried out in this paper, and the experimental results show that, compared with the existing revocation schemes, although our scheme increases the computational load of storage service provider (CSP) in order to achieve the attribute revocation, it does not need the participation of attribute authority (AA), which reduces the computational load of AA. Moreover, the user does not need any additional parameters to achieve the attribute revocation except for the private key, thus saving the storage space greatly.
Session Based Ciphertext Policy Attribute Based Encryption Method for Access Control in Cloud Storage