Efficient User Revocation in the Cloud

In cloud computing user can easily share and modify data inside group. Here data integrity can be easily ensured by using the public signature of existing users in the cloud group. By using data sharing services in cloud user can able modify data as a group on cloud. Integrity of these services can be improved using signature of public existing users on group. Shared data is divided into blocks. All user are responsible for modifying data on different blocks. When any user shows malicious activity in group then that user must be revoked for security purpose. So the block modified by that user must be re-sign by existing users in group. Traditional way to re-sign this is to down load part of data and re-sign it at the time of revocation of user. But this approach is not efficient for large amount of data being shared. This paper gives novel method for auditing integrity of shared data and provide effective way for user revocation. It uses the concept of proxy re-signature to avoid the downloading of re-signed block by existing user.