A Secure Anti-Collusion File Sharing System for Untrusted Cloud Storage

Abstract

In recent years, cloud has emerged as a collaborative computing platform and it is essential to share the data among multiple users of a group. As organizations outsource the storage of data files on the cloud, security guarantees becomes a main constraint. As the data is shared among collaborative members of the group, preserving the privacy of data is a challenging task due to frequent changes in group membership. Hence, in an untrusted cloud environment, it is necessary to protect the data against collusion attack and avoid the revoked user of the group to access original data. In practice, it is difficult for the group manager to update all the files with a new key whenever a user is added or removed from the group. As the updated files are stored in the cloud storage, it leads to duplication of files. In this paper, a secure anti-collusion file sharing system is developed to protect the data against collusion attack and a deduplication scheme is presented to avoid duplication of files and utilize the cloud storage efficiently. In this work, the key distribution among dynamic group members is done without a secure communication channel. Any authorized user can get the individual key from group manager and after user’s private key gets activated, the user is permitted to access the files of the group. In the proposed scheme, the revoked users are not permitted to access the files present in the cloud.