B-FLACS: blockchain-based flexible lightweight access control scheme for data sharing in cloud

Cloud storage provides convenience for data owners. But it faces serious challenges from data tampering and abuse. Flexible access control method is an effective way to protect shared data security. Existing attribute-based access control methods attempt to improve the access flexibility and security of shared data. But there are some problems for resourcelimited lightweight devices as performance and security to be solved. Blockchain can construct a trusted network for data owner to deal with data validity and digital forensics. This paper proposes a novel blockchain-based lightweight access control scheme. The proposed scheme uses blockchain to construct a trusted sharing network by consensus mechanism. The lightweight attribute-based sharing scheme is used to support fine-grained access control of data. In this scheme, it obfuscates the access control policy with fuzzy attribute set to improve system security, and reduces the computing complexity of system users by outsourcing complex operations to semi-trusted proxy servers. The security analysis shows that the scheme is ((S, rho), n - 1, epsilon)-secure against collusion attack between users and attribute authorities. The performance analysis results show that the proposed scheme reduces the computational complexity of user devices and provides faster response time compared with benchmark and state-of-the-art technologies.