On the (In)security of Hash-based Oblivious RAM and a New Balancing Scheme

Oblivious RAM (ORAM) is a provable technique to protect a user's access pattern to outsourced data. Recently, many ORAM constructions have been proposed, but most of them are impractical due to high communication and user-side storage costs. Motivated by Partition ORAM (P-ORAM) [16], a stateof-the-art communication-efficient ORAM construction, this paper proposes GPORAM (Generalized Partition ORAM) as a new framework to assemble multiple ORAM partitions together while overcoming the limitations of the P-ORAM construction. GP-ORAM allows smaller and adjustable number of partitions, fully utilizes the available user-side storage to reduce communication cost, and can efficiently export the index table to the server. As a result, GP-ORAM incurs low bandwidth cost (i.e., O(logN) data blocks per query in practice) and has significantly less user-side storage cost than P-ORAM.We demonstrate the security and practicality of GP-ORAM through extensive performance analysis. , a stateof-the-art communication-efficient ORAM construction, this paper proposes GP-ORAM (Generalized Partition ORAM) as a new framework to assemble multiple ORAM partitions together while overcoming the limitations of the P-ORAM construction. GP-ORAM allows smaller and adjustable number of partitions, fully utilizes the available user-side storage to reduce communication cost, and can efficiently export the index table to the server. As a result, GP-ORAM incurs low bandwidth cost (i.e., O(log N ) data blocks per query in practice) and has significantly less user-side storage cost than P-ORAM. We demonstrate the security and practicality of GP-ORAM through extensive performance analysis.

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“…[3][4][5][6][7][8][9][10]12,14]. These ORAMs only have little state information, such as secret keys and query counters, stored in local storage.…”

Section: Related Workmentioning

confidence: 99%

“…These ORAMs only have little state information, such as secret keys and query counters, stored in local storage. Among them, Balanced ORAM (B-ORAM) [9] proposed by Kushilevitz et. al.…”

Section: Related Workmentioning

confidence: 99%

GP-ORAM: A Generalized Partition ORAM

Zhang

Qiao

2015

Network and System Security

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“…Oblivious RAM (ORAM) was first proposed by Goldreich and Ostrovsky [21], and later improved in a series of works [13,14,17,20,[22][23][24]26,[28][29][30][31][33][34][35][36][37]. Recently, ORAM has been used in outsourcing storage [22,35,37], and in secure two-party computation to achieve sublinear amortized cost [17,25].…”

Section: Related Workmentioning

confidence: 99%

“…In Section 4, we give two specific VOS schemes -Path VOS and Hierarchical VOS. These are derived from the two classes of ORAM schemes, the hierarchical construction [21] and its variants [22,24,26,30,[35][36][37], and the binary-tree scheme [31] and its variants [13,17,34].…”

Section: Oram To Vos: Generic Compilation Techniquesmentioning

confidence: 99%

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Verifiable Oblivious Storage

Apon

Katz

Shi

et al. 2014

Lecture Notes in Computer Science

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We formalize the notion of Verifiable Oblivious Storage (VOS), where a client outsources the storage of data to a server while ensuring data confidentiality, access pattern privacy, and integrity and freshness of data accesses. VOS generalizes the notion of Oblivious RAM (ORAM) in that it allows the server to perform computation, and also explicitly considers data integrity and freshness.We show that allowing server-side computation enables us to construct asymptotically more efficient VOS schemes whose bandwidth overhead cannot be matched by any ORAM scheme, due to a known lower bound by Goldreich and Ostrovsky. Specifically, for large block sizes we can construct a VOS scheme with constant bandwidth per query; further, answering queries requires only poly-logarithmic server computation. We describe applications of VOS to Dynamic Proofs of Retrievability, and RAM-model secure multi-party computation.

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