Security-Efficiency Tradeoffs in Searchable Encryption

Authors: Raphael Bost (Direction Générale de l’Armement - Maîtrise de l’Information. The views and conclusions contained herein are those of the author and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the DGA or the French Government.), Pierre-Alain Fouque (Université de Rennes 1, France.)

Volume: 2019
Issue: 4
Pages: 132–151

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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.

Keywords: Searchable Encryption; Lower Bounds;

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