SECURE AND COST EFFECTIVE USER REVOCATION MECHANISM FOR DATA ANALYSIS IN THE CLOUD

In the cloud, users can easily share and modify the data as a group using the data storage and sharing services. To make certain shared information, integrity can be checked publicly; users in the organization need to compute signatures on the maximum of the blocks in shared data. Various blocks in shared data are regularly signed by different customers as a result of modifications done by various users. For security reasons, as soon as a person is revoked from the organization, the blocks which have been formally signed by using this revoked user should be re-signed by a pre-existing user. The best technique, permitting a pre-existing user to download the corresponding part of shared records and re-sign it at some stage in user revocation, is inefficient because of the huge size of shared data in the cloud. In this, we propose a secure and cost-effective user revocation mechanism for data analysis in the cloud. With the help of proxy re-signatures at revocation, we permit the cloud to re-sign blocks for existing customers, to ensure that existing users do not require to save and re-sign blocks again. In addition, a public verifier is used to check the integrity of public data without retrieving the whole data from the cloud, in spite of the fact that some amount of shared data has been re-signed by using the cloud. Additionally, this mechanism can support group auditing by validating many auditing tasks simultaneously.