Abstract: The ciphertext policy-based attribute encryption scheme (CP-ABE) provides secure and fine-grained access control for cloud storage systems. However, due to the large amount of bilinear pairing operation in the encryption and decryption algorithm, it brings a heavy burden to the users. In order to solve the above problems, a verifiable attribute-based encryption scheme supporting outsourced decryption in fog computing is proposed. In the scheme, the linear secret sharing scheme is used to construct the access matrix, which can express various forms of access policies flexibly. Part of the decryption operations is outsourced to fog nodes, so as to reduce the computing burden of the client. To enhance the credibility of outsourced fog nodes, the correctness of the ciphertext accessed by fog nodes is verified through blockchain transactions, and the access behaviors cannot be denied. Through security and experimental analysis, it is proved that the scheme can resist selective plaintext attack and has high operation efficiency.

Key words: attribute-based encryption, fog computing, outsourced decryption, blockchain