Securely outsourcing exponentiations with single untrusted program for cloud storage

Abstract

Provable Data Possession (PDP) allows a file owner to outsource her files to a storage server such that a verifier can check the integrity of the outsourced file. Public verifiable PDP schemes allow any one other than the file owner to be a verifier. At the client side (file owner or verifier), a substantial number of modular exponentiations is often required. In this paper we make PDP more practical via proposing a protocol to securely outsource the (most generic) variable-exponent variable-base exponentiations in one untrusted program model. Our protocol demonstrates advantages in efficiency or privacy over existing protocols coping with only special cases in two or single untrusted program model. We then apply our generic protocol to Shacham-Waters PDP and a variant of Yuan-Yu PDP. The analyses show that our protocol makes PDP much more efficient at the client side. © 2014 Springer International Publishing Switzerland.