In this work we identify attacks that exploit client-side deduplication, allowing an attacker to gain access to potentially huge files of other users based on a very small amount of side information. For example, an attacker who knows the hash signature of a file can convince the storage service that it owns that file, hence the server later lets the attacker download the entire file.
To overcome such attacks, we introduce proofs-of-ownership (PoWs), where a client proves to the server that it actually holds the data of the file and not just some short information about it. We formalize proof-of-ownership, present solutions based on Merkle trees and specific encodings, and analyze their security. We implemented one variant of the scheme, our performance measurements indicate that our protocol incurs only a small overhead (compared to naive client-side deduplication that is vulnerable to the attack).Category / Keywords: applications / Cloud storage, deduplication, proofs-or-knowledge, proofs-of-retrievability Publication Info: Extended abstract appears in ACM CCS 2011 Date: received 29 Apr 2011, last revised 11 Aug 2011 Contact author: shaih at alum mit edu Available format(s): PDF | BibTeX Citation Version: 20110811:135308 (All versions of this report) Discussion forum: Show discussion | Start new discussion