Cryptology ePrint Archive: Report 2016/543

ObliviSync: Practical Oblivious File Backup and Synchronization

Adam J. Aviv and Seung Geol Choi and Travis Mayberry and Daniel S. Roche

Abstract: Oblivious RAM (ORAM) protocols are powerful techniques that hide a client's data as well as access patterns from untrusted service providers. We present an oblivious cloud storage system, ObliviSync, that specifically targets one of the most widely-used personal cloud storage paradigms: synchronization and backup services, popular examples of which are Dropbox, iCloud Drive, and Google Drive. This setting provides a unique opportunity because the above privacy properties can be achieved with a simpler form of ORAM called write-only ORAM, which allows for dramatically increased efficiency compared to related work. Our solution is asymptotically optimal and practically efficient, with a small constant overhead of approximately 4x compared with non-private file storage, depending only on the total data size and parameters chosen according to the usage rate, and not on the number or size of individual files. Our construction also offers protection against timing-channel attacks, which has not been previously considered in ORAM protocols. We built and evaluated a full implementation of ObliviSync that supports multiple simultaneous read-only clients and a single concurrent read/write client whose edits automatically and seamlessly propagate to the readers. We show that our system functions under high work loads, with realistic file size distributions, and with small additional latency (as compared to a baseline encrypted file system) when paired with Dropbox as the synchronization service.

Category / Keywords: applications / Oblivious RAM, cloud services, privacy

Original Publication (with minor differences): NDSS 2017

Date: received 31 May 2016, last revised 2 Dec 2016

Contact author: roche at usna edu

Available format(s): PDF | BibTeX Citation

Version: 20161202:203048 (All versions of this report)

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