A Blockchain-based access control scheme with multiple attribute authorities for secure cloud data sharing

Ciphertext-policy attribute-based encryption(CP-ABE) has been widely studied and used in access control schemes for secure data sharing. Since in most of the existing attribute-based encryption methods, all user attributes are managed by a single central authority, it is easy to cause a single point of failure. Therefore, several multi-authority CP-ABE schemes are proposed to manage user attributes by multiple authorities. However, these schemes still do not eliminate the single point of failure in essence or suffer from high computation and communication overhead on data users. In this paper, we propose a Blockchain-based Multi-authority Access Control scheme called BMAC for sharing data securely. Shamir secret sharing scheme and permissioned blockchain (Hyperledger Fabric) are introduced to implement that each attribute is jointly managed by multiple authorities to avoid single point of failure. In addition, we take advantage of blockchain technology to establish trust among multiple authorities and exploit smart contracts to compute tokens for attributes managed across multiple management domains, which reduces communication and computation overhead on the data user side. Moreover, blockchain helps to record the access control process in a secure and auditable way. Finally, we analyze the security of the proposed algorithm. Further analysis and comparison show the performance of the proposed method.