Locality-preserving oblivious RAM

Gilad Asharov, T. H. Hubert Chan, Kartik Nayak, Rafael Pass, Ling Ren, Elaine Shi

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

6 Scopus citations


Oblivious RAMs, introduced by Goldreich and Ostrovsky [JACM’96], compile any RAM program into one that is “memory oblivious”, i.e., the access pattern to the memory is independent of the input. All previous ORAM schemes, however, completely break the locality of data accesses (for instance, by shuffling the data to pseudorandom positions in memory). In this work, we initiate the study of locality-preserving ORAMs—ORAMs that preserve locality of the accessed memory regions, while leaking only the lengths of contiguous memory regions accessed. Our main results demonstrate the existence of a locality-preserving ORAM with poly-logarithmic overhead both in terms of bandwidth and locality. We also study the tradeoff between locality, bandwidth and leakage, and show that any scheme that preserves locality and does not leak the lengths of the contiguous memory regions accessed, suffers from prohibitive bandwidth. To the best of our knowledge, before our work, the only works combining locality and obliviousness were for symmetric searchable encryption [e.g., Cash and Tessaro (EUROCRYPT’14), Asharov et al. (STOC’16)]. Symmetric search encryption ensures obliviousness if each keyword is searched only once, whereas ORAM provides obliviousness to any input program. Thus, our work generalizes that line of work to the much more challenging task of preserving locality in ORAMs.

Original languageEnglish
Title of host publicationAdvances in Cryptology – EUROCRYPT 2019 - 38th Annual International Conference on the Theory and Applications of Cryptographic Techniques, Proceedings
EditorsYuval Ishai, Vincent Rijmen
PublisherSpringer Verlag
Number of pages30
ISBN (Print)9783030176556
StatePublished - 2019
Externally publishedYes
Event38th Annual International Conference on the Theory and Applications of Cryptographic Techniques, Eurocrypt 2019 - Darmstadt, Germany
Duration: 19 May 201923 May 2019

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume11477 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference38th Annual International Conference on the Theory and Applications of Cryptographic Techniques, Eurocrypt 2019

Bibliographical note

Funding Information:
Acknowledgments. This work was partially supported by a Junior Fellow award from the Simons Foundation to Gilad Asharov. This work was supported in part by NSF grants CNS-1314857, CNS-1514261, CNS-1544613, CNS-1561209, CNS-1601879, CNS-1617676, an Office of Naval Research Young Investigator Program Award, a Packard Fellowship, a Sloan Fellowship, Google Faculty Research Awards, a VMWare Research Award, and a Baidu Faculty Research Award to Elaine Shi. Kartik Nayak was partially supported by a Google Ph.D. Fellowship Award. T.-H. Hubert Chan was partially supported by the Hong Kong RGC under the grant 17200418.

Publisher Copyright:
© International Association for Cryptologic Research 2019.


  • Locality
  • Oblivious RAM
  • Randomized algorithms


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