Searchable symmetric encryption: Optimal locality in linear space via two-dimensional balanced allocations

Gilad Asharov, Moni Naor, Gil Segev, Ido Shahaf

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

80 Scopus citations

Abstract

Searchable symmetric encryption (SSE) enables a client to store a database on an untrusted server while supporting keyword search in a secure manner. Despite the rapidly increasing interest in SSE technology, experiments indicate that the performance of the known schemes scales badly to large databases. Somewhat surprisingly, this is not due to their usage of cryptographic tools, but rather due to their poor locality (where locality is defined as the number of noncontiguous memory locations the server accesses with each query). The only known schemes that do not suffer from poor locality suffer either from an impractical space overhead or from an impractical read efficiency (where read efficiency is defined as the ratio between the number of bits the server reads with each query and the actual size of the answer). We construct the first SSE schemes that simultaneously enjoy optimal locality, optimal space overhead, and nearlyoptimal read efficiency. Specifically, for a database of size N, under the modest assumption that no keyword appears in more than N1-1/log log N documents, we construct a scheme with read efficiency Õ(log log N). This essentially matches the lower bound of Cash and Tessaro (EUROCRYPT'14) showing that any SSE scheme must be sub-optimal in either its locality, its space overhead, or its read efficiency. In addition, even without making any assumptions on the structure of the database, we construct a scheme with read efficiency Õ(log N). Our schemes are obtained via a two-dimensional generalization of the classic balanced allocations ("balls and bins") problem that we put forward. We construct nearly-optimal two-dimensional balanced allocation schemes, and then combine their algorithmic structure with subtle cryptographic techniques.

Original languageEnglish
Title of host publicationSTOC 2016 - Proceedings of the 48th Annual ACM SIGACT Symposium on Theory of Computing
EditorsYishay Mansour, Daniel Wichs
PublisherAssociation for Computing Machinery
Pages1101-1114
Number of pages14
ISBN (Electronic)9781450341325
DOIs
StatePublished - 19 Jun 2016
Externally publishedYes
Event48th Annual ACM SIGACT Symposium on Theory of Computing, STOC 2016 - Cambridge, United States
Duration: 19 Jun 201621 Jun 2016

Publication series

NameProceedings of the Annual ACM Symposium on Theory of Computing
Volume19-21-June-2016
ISSN (Print)0737-8017

Conference

Conference48th Annual ACM SIGACT Symposium on Theory of Computing, STOC 2016
Country/TerritoryUnited States
CityCambridge
Period19/06/1621/06/16

Bibliographical note

Publisher Copyright:
© 2016 ACM. 978-1-4503-4132-5/16/06...$15.00.

Funding

FundersFunder number
Horizon 2020 Framework Programme714253, 891234

    Keywords

    • Balanced allocations
    • Cryptography
    • Searchable encryption

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