Group-oriented Proofs of Storage

Abstract

We introduce and formalize the notion of group-oriented proofs of storage (GPoS). In GPoS, each file owner, after being authorized as a member by a group manager, can outsource files to a group storage account maintained by an untrusted party, for example, a cloud storage server, while anyone can efficiently verify the integrity of the remotely stored files without seeing the files. The file owner's identity privacy is preserved against the cloud server while the group manager can trace the one who outsourced any suspicious file for liability investigation. By novelly identifying and exploiting several useful properties, that is, homomorphic composability and homomorphic verifiability in some signatures, we propose a generic GPoS construction relying on the security of the underlying signature scheme and the hardness of the computational Diffie-Hellman (CDH) problem. Following the generic construction, we instantiate a concrete GPoS scheme with the well-known Boneh-Boyen short signature. By leveraging the polynomial commitment technique, the proposed GPoS proposal is optimized with constant-size bandwidth consumption in proof of storage by the cloud server. Theoretical analyses and comparisons show that our GPoS proposal is advantageous over existing PoS-like schemes in user privacy, public audibility and/or performance in a multi-user setting.