Cryptology ePrint Archive: Report 2019/693

Security-Efficiency Tradeoffs in Searchable Encryption -- Lower Bounds and Optimal Constructions

Raphael Bost and Pierre-Alain Fouque

Abstract: Besides their security, the efficiency of searchable encryption schemes is a major criteria when it comes to their adoption: in order to replace an unencrypted database by a more secure construction, it must scale to the systems which rely on it. Unfortunately, the relationship between the efficiency and the security of searchable encryption has not been widely studied, and the minimum cost of some crucial security properties is still unclear. In this paper, we present new lower bounds on the tradeoffs between the size of the client state, the efficiency and the security for searchable encryption schemes. These lower bounds target two kinds of schemes: schemes hiding the repetition of search queries, and forward-private dynamic schemes, for which updates are oblivious. We also show that these lower bounds are tight, by either constructing schemes matching them, or by showing that even a small increase in the amount of leaked information allows for constructing schemes breaking the lower bounds.

Category / Keywords: foundations / searchable encryption, lower bound

Original Publication (with minor differences): PoPETS 2019

Date: received 11 Jun 2019, last revised 1 Aug 2019

Contact author: raphael_bost at alumni brown edu

Available format(s): PDF | BibTeX Citation

Version: 20190802:054619 (All versions of this report)

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