Oblivious Parallel RAM: Improved Efficiency and Generic Constructions

In this work, we investigate if statistical privacy can enhance the performance of ORAM mechanisms while providing rigorous privacy guarantees. We propose a formal and rigorous framework for developing ORAM protocols with statistical security viz., a differentially private ORAM (DP-ORAM). We present Root ORAM, a family of DP-ORAMs that provide a tunable, multi-dimensional trade-off between the desired bandwidth overhead, local storage and system security. We theoretically analyze Root ORAM to quantify both its security and performance. We experimentally demonstrate the benefits of Root ORAM and find that (1) Root ORAM can reduce local storage overhead by about 2× for a reasonable values of privacy budget, significantly enhancing performance in memory limited platforms such as trusted execution environments, and (2) Root ORAM allows tunable trade-offs between bandwidth, storage, and privacy, reducing bandwidth overheads by up to 2×-10× (at the cost of increased storage/statistical privacy), enabling significant reductions in ORAM access latencies for cloud environments. We also analyze the privacy guarantees of DP-ORAMs through the lens of information theoretic metrics of Shannon entropy and Min-entropy [16]. Finally, Root ORAM is ideally suited for applications which have a similar access pattern, and we showcase its utility via the application of Private Information Retrieval.

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“…Pr st[O Z k,p (s)] > R + Z · 2 k ≤ 14(0.6002) R (14) This completes the proof of the stash bounds 12 .…”

Section: Proof Of Theoremmentioning

confidence: 56%

“…al. [14] build on [55] and extend it for multiple clients by level caching in tree based ORAM schemes. Root ORAM generalizes the construction of [55] to provide a tunable framework offering DP-ORAM guarantees.…”

Section: Related Workmentioning

confidence: 99%

Differentially Private Oblivious RAM

Wagh

Cuff

Mittal

2018

Proceedings on Privacy Enhancing Technologies

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“…We note that IR, RAM and KVS are the most studied storage primitives to provide oblivious access. There are many other extensions to these primitives that have also been studied [9,10,13,16,17,29,31,38].…”

Section: Storage Primitivesmentioning

confidence: 99%

What Storage Access Privacy is Achievable with Small Overhead?

Patel

Persiano

Yeo

2019

Proceedings of the 38th ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems

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Oblivious RAM (ORAM) and private information retrieval (PIR) are classic cryptographic primitives used to hide the access pattern to data whose storage has been outsourced to an untrusted server. Unfortunately, both primitives require considerable overhead compared to plaintext access. For large-scale storage infrastructure with highly frequent access requests, the degradation in response time and the exorbitant increase in resource costs incurred by either ORAM or PIR prevent their usage. In an ideal scenario, a privacypreserving storage protocols with small overhead would be implemented for these heavily trafficked storage systems to avoid negatively impacting either performance and/or costs. In this work, we study the problem of the best storage access privacy that is achievable with only small overhead over plaintext access.To answer this question, we consider differential privacy access which is a generalization of the oblivious access security notion that are considered by ORAM and PIR. Quite surprisingly, we present strong evidence that constant overhead storage schemes may only be achieved with privacy budgets of ϵ = Ω(log n). We present asymptotically optimal constructions for differentially private variants of both ORAM and PIR with privacy budgets ϵ = Θ(log n) with only O(1) overhead. In addition, we consider a more complex storage primitive called key-value storage in which data is indexed by keys from a large universe (as opposed to consecutive integers in ORAM and PIR). We present a differentially private key-value storage scheme with ϵ = Θ(log n) and O(log log n) overhead. This construction uses a new oblivious, two-choice hashing scheme that may be of independent interest.

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“…Recently, Chen, Lin, and Tessaro [CLT16] showed a more efficient OPRAM compiler, as well as a generic transformation taking any generic ORAM compiler to an OPRAM compiler. However, the compilers of [CLT16] only apply to PRAM programs with a fixed number of CPUs. Boyle et al [BCP16] also constructed the first (non-succinct) garbling PRAM schemes based on identitybased encryptions.…”

Section: Related Workmentioning

confidence: 99%

Cryptography for Parallel RAM from Indistinguishability Obfuscation

Chow

Chung

Lai

et al. 2016

Proceedings of the 2016 ACM Conference on Innovations in Theoretical Computer Science

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Since many cryptographic schemes are about performing computation on data, it is important to consider a computation model which captures the prominent features of modern system architecture. Parallel random access machine (PRAM) is such an abstraction which not only models multiprocessor platforms, but also new frameworks supporting massive parallel computation such as MapReduce.In this work, we explore the feasibility of designing cryptographic solutions for the PRAM model of computation to achieve security while leveraging the power of parallelism and random data access. We demonstrate asymptotically optimal solutions for a wide-range of cryptographic tasks based on indistinguishability obfuscation. In particular, we construct the first publicly verifiable delegation scheme with privacy in the persistent database setting, which allows a client to privately delegate both computation and data to a server with optimal efficiency. Specifically, the server can perform PRAM computation on private data with parallel efficiency preserved (up to poly-logarithmic overhead). Our results also cover succinct randomized encoding, searchable * A full version is available at encryption, functional encryption, secure multiparty computation, and indistinguishability obfuscation for PRAM.We obtain our results in a modular way through a notion of computational-trace indistinguishability obfuscation (CiO), which may be of independent interests.

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Oblivious Parallel RAM: Improved Efficiency and Generic Constructions

Cited by 38 publications

References 18 publications

Differentially Private Oblivious RAM

Differentially Private Oblivious RAM

What Storage Access Privacy is Achievable with Small Overhead?

Cryptography for Parallel RAM from Indistinguishability Obfuscation

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