Abstract
Cloud storage serves as a cost-effective way of storing and sharing data among individuals. The cloud environment cannot be trusted always because of the threats caused by users and other machines in the cloud. Outsourcing data to cloud environment entails serious security concern. In recent trends, group sharing of data in public cloud is a major issue. In order to overcome this issue, a novel method to share the data among user groups securely and efficiently is proposed. The system utilizes Shamir's (k, n) threshold scheme to securely manage the keys, where the k out of n shares are required to generate the key and multiple Key Managers each having one share of keys and this avoids single point failure of cryptographic keys. By adding timestamp parameter to the Group User List (GUL), secure user revocation can be attained, so that deleted user cannot access the data in the revoked group and supports dynamic groups. For secure transmission of keys to the Group Members, a session key (lambda(x))(y) is established between each of the entities considered. The proposed system is implemented and tested for file uploading and downloading, key generation and key establishment time. The results prove that the proposed system can be used as an effective tool for group data sharing.