An efficient and revocable attribute-based data sharing scheme with rich expression and escrow freedom

Attribute-based encryption effectively realizes fine-grained access control by using attributes. It provides an ideal access control strategy for new computing environments with large-scale, strong dynamics and strong privacy characteristics, such as cloud computing and the Internet of things. In this paper, we propose an efficient and provably secure cloud data sharing scheme (ABEDS-RR) using ciphertext policy attributed-based encryption. The ABEDS-RR scheme needs a semi-trusted proxy party to transform part of the ciphertext with a conversion key. Compared with most existing schemes, when changing the attributes of a user, only the private key and conversion key of the user need to be modified. In order to better adapt to occasions with limited computing capacity, such as ad hoc network, smart sensor, mobile device, the scheme can be extended to the case of outsourcing decryption. In addition, the ABEDS-RR scheme overcomes key escrow issues by co-generating user keys between two entities, and enriches the expression ability of attributes by introducing weight attributes.