Ciphertext-Policy Attribute-Based Encryption (CP-ABE) is similar to role-based access control

which provides flexible and fine-grained access control for cloud storage systems. However

in most of existing CP-ABE schemes

the ciphertext length is positively related to the complexity of the access structure. And the attribute level user revocation is an important challenge because the system attributes are shared by multiple users at the same time. To solve this problem

this paper presents an CP-ABE scheme that supports the attribute level user revocation and constant-size ciphertext. The attribute group key for each user in the scheme is different

so this scheme can effectively resist collusion attacks between the revoked users and the existing users. To reduce the computational burden of the attribute authority and the data owner

the amount of computation required for the attribute revocation process is outsourced to the data service manager. At the same time

the scheme adopts the AND-Gate strategy supporting multi-valued attributes and wildcards

and the ciphertext length is constant. The scheme is proved selectively secure based on Decisional q-Bilinear Diffie-Hellman Exponent (q-BDHE) assumption. Finally

the functionality and efficiency of the proposed scheme are analyzed and verified. The experimental results show that the proposed scheme can safely implement attribute level user revocation. At the same time

the proposed scheme has some advantages in terms of function and computational efficiency. It is suitable for practical application.