An access control scheme with fine-grained time constrained attributes based on smart contract and trapdoor

Attribute-based encryption describes the access policy with the attribute information of users. In practice, attributes usually have a certain lifespan. The existing time-based access control methods directly relate attribute keys to time. Thus, under the constraint of fine-grained time, when the attribute expires, the update of key and policy adds a large additional burden to the data user and owner. In this paper, we propose a dynamic attribute-based access control scheme to set a fine-grained valid time period for each attribute, which not only facilitates dynamic data sharing, but also enables flexible attribute revocation. We use smart contract to set valid time period for attributes. It provides smart management on users' attributes and avoids the waiting time of CSP caused by manual operations. We also introduce trapdoor that are indirectly related to time and proxy decryption method to reduce computational cost on data owners and users. Extensive security and performance analysis shows the security strength and effectiveness of the proposed scheme.