Insecurity of a Public Proof of Cloud Storage from Lattice Assumption

Cloud storage auditing is considered as a significant service to verify the integrity of the data stored in cloud. Liu et al. have proposed a proof of storage protocol with public auditing form lattice assumption, which can resist quantum computer attacks. They claim that the protocol enjoys desirable security properties, such as unforgeability and privacy preserving. We demonstrate that any malicious cloud service provider can cheat the third party auditor and the users, through generating the valid response proof which can pass the verification even if some other data blocks are lost by accident. And the primitive data blocks maybe recovered by any curious third party auditor through solving some linearly equations. Our work can help cryptographers and engineers design and implement more secure and efficient lattice-based public auditing scheme for the cloud storage data.