To achieve privacy-preserving public auditing, we propose to uniquely integrate the homomorphic linear authenticator with random masking technique. In our protocol, the linear combination of sampled blocks in the server’s response is masked with randomness generated the server. With random masking, the TPA no longer has all the necessary information to build up a correct group of linear equations and therefore cannot derive the user’s data content, no matter how many linear combinations of the same set of file blocks can be collected. On the other hand, the correctness validation of the blockauthenticator pairs can still be carried out in a new way which will be shown shortly, even with the presence of the randomness. Our design makes use of a public key based HLA, to equip the auditing protocol with public auditability. The first to consider public auditability in their defined “provable data possession” (PDP) model for ensuring possession of data files on untrusted storages. Their scheme utilizes the RSAbased homomorphic linear authenticators for auditing outsourced data and suggests randomly sampling a few blocks of the file. The public auditability in their scheme demands the linear combination of sampled blocks exposed to external auditor. When used directly, their protocol is not provably privacy preserving, and thus may leak user data information to the auditor.