Cryptology ePrint Archive: Report 2017/046

Practical Passive Leakage-Abuse Attacks Against Symmetric Searchable Encryption

Matthieu Giraud and Alexandre Anzala-Yamajako and Olivier Bernard and Pascal Lafourcade

Abstract: Symmetric Searchable Encryption (SSE) schemes solve efficiently the problem of securely outsourcing client data with search functionality. These schemes are provably secure with respect to an explicit leakage profile; however, determining how much information can be inferred in practice from this leakage remains difficult. First, we recall the leakage hierarchy introduced in 2015 by Cash et al. Second, we present complete practical attacks on SSE schemes of L4, L3 and L2 leakage profiles which are deployed in commercial cloud solutions. Our attacks are passive and only assume the knowledge of a small sample of plaintexts. Moreover, we show their devastating effect on real-world data sets since, regardless of the leakage profile, an adversary knowing a mere 1% of the document set is able to retrieve 90% of documents whose content is revealed over 70%. Then, we further extend the analysis of existing attacks to highlight the gap of security that exists between L2- and L1-SSE and give some simple countermeasures to prevent our attacks.

Category / Keywords: symmetric searchable encryption, leakage, passive attacks

Original Publication (with minor differences): SECRYPT 2017

Date: received 20 Jan 2017, last revised 8 Jun 2017

Contact author: matthieu giraud at uca fr

Available format(s): PDF | BibTeX Citation

Version: 20170608:161641 (All versions of this report)

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