A secure, traceable, and efficiently revocable cloud-based access control scheme using ciphertext policy attribute-based encryption and blockchain

Ciphertext Policy Attributed-based Encryption (CP-ABE) is considered as a suitable solution for supporting secure and fine-grained access control for outsourced data. Considering the revocation problem in cloud-based access control, existing revocable CP-ABE based schemes still have limitations. First, most solutions did not support both user and attribute revocation with auditability of revocation transactions. Second, they still relied on data owners or data users to generate the crypto components such as ciphertext update key to support the revocation process, resulting in the dependency of the availability of the data owner and computation overhead in both the data owner and the data user. Third, they did not provide the formal procedure for invoking the affected ciphertexts. Finally, most of them did not tackle the attributes hiding to support privacy-preserving policy outsourcing. To this end, we proposed a cloud-based access control scheme by leveraging CP-ABE, AES symmetric encryption, and blockchain technology to deliver an efficient user and attribute revocation with the ciphertext retrieval mechanism and transaction traceability. In addition, we introduced the attribute hiding method based on hidden vector encryption (HVE) to preserve the privacy of access policy content. To evaluate the efficiency of our proposed scheme, we conducted experiments to show that our proposed scheme is efficient and practical for real implementation.