https://www.cis.temple.edu/~jiewu/research/publications/Publication_files/INS-Time-Based%20Proxy%20Re-encryption%20Scheme%20for%20Secure%20Data%20Sharing%20in%20a%20Cloud%20Environment.pdf
Abstract A fundamental approach for secure data sharing in a cloud environment is to let the data owner encrypt data before outsouring. To simultaneously achieve fine-grained access control on encrypted data and scalable user revo-cation, existing work combines attribute-based encryption (ABE) and proxy re-encryption (PRE) to delegate the cloud service provider (CSP) to execute re-encryption ...