Performance Enhanceduser Revocation for Shared Resource Incloud

Data can be shared and stored in the cloud, user can modify easily and share data as a group. The data integrity can be verified, users in the group need to compute signature on the block in the shared data are signed by different user. For security purpose, after the user is revoked from the group, the blocks which were previously signed by this revoked user must be resigned automatically. In the previous method, user need to download the shared data and re-sign it during user revocation, it is inefficient. It does not support the time performance during the user revocation in the previous method. As a result this mechanism improve the efficiency and time performance during user revocation.