A revocable storage CP-ABE scheme with constant ciphertext length in cloud storage.

Abstract

The ciphertext policy attribute-based encryption (CP-ABE) is widely used in cloud storage. It not only provides a secure data sharing scheme but also has the characteristics of fine-grained access control. However, most CP-ABE schemes have problems such as the ciphertext length increases with the complexity of the access policy, the encryption scheme is complex, the computational efficiency is low, and the fine-grained revocation cannot be performed. In view of the above problems, this pa-per proposes an efficient CP-ABE scheme with fine-grained revocable storage and constant ciphertext length. The scheme combines proxy re-encryption with CP-ABE technology, adopts the flexible access strategy AND-gates on multi-valued attributes with wildcards (AND∗m ), and realizes revocable storage and fixed-length ciphertext. At the same time, in order to reduce the amount of user decryption calcu-lation, the complex operation in the decryption process is outsourced to the third-party server and the decryption result is verified to ensure the correctness of the information. Finally, the security of the scheme is proved under the decisional bilinear Diffie-Hellman (DBDH) assumption. In addition, the performance analysis shows that the scheme is efficient and feasible in cloud storage.