Used mainly for the virtual money, the Blockchain technology adopts a decentralized network of peers to ensure a secure and transparent information storage and transmission. The basic use of Blockchain can be bypassed, and it is interesting to integrate it into other fields such as the Cloud storage. Cloud storage solutions ensure a continuous data synchronization and guarantee data sharing between different users. However, sharing user side encrypted data raises key and access control management challenges. Within this paper, we propose a novel access control model called Timely CP-ABE. Two main features come with our model. First, we introduce a decentralized access control mechanism where the user legitimacy is verified by Blockchain nodes. Second, we add temporal dimension to file sharing based on CP-ABE. In fact, we introduce a validity time to the access authorization without additional revocation cost. As a proof of concept, the implementation of the Timely CP-ABE based on Blockchain is performed on the CP-ABE toolkit and Multichain solution.