A NOVEL PUBLIC AUDITING MECHANISM FOR THE INTEGRITY OF SHARED DATA WITH EFFICIENT USER REVOCATION IN THE CLOUD

In this abstract, we propose Panda, a novel public auditing mechanism for the integrity of shared data with efficient user revocation in t he cloud. In our mechanism, by utilizing the idea of proxy re-signatures, once a user in the group is revoked, the cloud is able to re-sign the blocks, which were signed by the revoked user, with a re-signing key. As a result, the efficiency of user revocation can be significantly improved, and computation and communication resources of existing users can be easily saved. Meanwhile, the cloud, who is not in the same trusted domain with each user, is only able t o convert a signature of the revoked user into a signature of an existing user on the same block, but it cannot sign arbitrary blocks on behalf of either the revoked user or an existing user. By designing anew proxy re-signature scheme with nice properties, which traditional proxy re-signatures do not have, our mechanism is always able to check the integrity of shared data without retrieving the entire data from the cloud. Experimental results show that our mechanism can significantly imp rove the efficiency of user revocation.