Panda : Public Auditing for Shared Data with Efficient User Revocation in The Cloud

Storage and sharing of data in the cloud can be easily modified by the users. So to overcome this shared data modification in the cloud, signature is being provided to each individual who access the data in cloud. Once the data is modified by the user on a block, the user must ensure that the signature is provided on that specific block. When a user gets revoked from the group, the blocks which were previously signed by this revoked user must be re-signed by an existing user. This straightforward method allows an existing user to download the entire data and re-sign it. But during user revocation, it is inefficient due to the large size of shared data in the cloud. In this paper, we propose a novel public auditing mechanism for the integrity of shared data with efficient user revocation. We utilize the idea of proxy re-signatures, we allow the cloud to re-sign blocks on behalf of existing users during user revocation. A public verifier is used to audit the integrity of shared data without retrieving the entire data from the cloud, even if some part of shared data has been re-signed by the cloud. Moreover, our mechanism supports batch auditing.