Decrypting shared encrypted data files stored in a cloud using dynamic key aggregation

Abstract

Cloud file sharing is a topic that has been in top flight for a long period of time and even in near future. Many methods like access control lists, attribute based encryption, identity based encryption and proxy re-encryption were introduced for sharing data stored in a cloud. But their drawbacks lead to the introduction of key aggregation based file sharing where the content provider generates an aggregate key based on files to be shared and distribute it among the users. Even though this mechanism is very much effective, it has the drawback that if once a user gets an aggregate key corresponding to a set of files from the data owner, then the data owner cannot revoke the permission for accessing the updated files to the user, who already possess the aggregate key. Our scheme in this paper provides an extension to this existing work which guarantees a dynamic generation of the aggregate key and thereby will not allow any unauthorised access to the updated files in the cloud.