On the Security of a Cloud Data Storage Auditing Protocol IPAD

Nowadays cloud data storage is a very important storage service for us, but to ensure the datum stored in the remote cloud server remains unmodified, we need a mechanism to check the datum's integrity, cloud data storage auditing protocol is such a mechanism, which has received great attention from researchers. Recently Zhang et al. proposed an efficient ID-based public auditing protocol called IPAD for the outsourced data by combing Waters signature and public auditing for the outsourced data. They claimed IPAD is the first ID-based auditing protocol for data integrity in the standard security model. But in this paper we show their proposal is not secure. Especially, the adversaries can easily generate tags for any file, which obviously break the unforgeability property of the cloud storage auditing protocol.