Cryptology ePrint Archive: Report 2013/330

Trapdoor Privacy in Asymmetric Searchable Encryption Schemes

Afonso Arriaga and Qiang Tang and Peter Ryan

Abstract: Asymmetric searchable encryption allows searches to be carried over ciphertexts, through delegation, and by means of trapdoors issued by the owner of the data. Public Key Encryption with Keyword Search (PEKS) is a primitive with such functionality that provides delegation of exact-match searches. As it is important that ciphertexts preserve data privacy, it is also important that trapdoors do not expose the user's search criteria. The difficulty of formalizing a security model for trapdoor privacy lies in the verification functionality, which gives the adversary the power of verifying if a trapdoor encodes a particular keyword. In this paper, we provide a broader view on what can be achieved regarding trapdoor privacy in asymmetric searchable encryption schemes, and bridge the gap between previous definitions, which give limited privacy guarantees in practice against search patterns. We propose the notion of Strong Search Pattern Privacy for PEKS and construct a scheme that achieves this security notion.

Category / Keywords: Asymmetric Searchable Encryption, PEKS, Trapdoor Privacy, Anonymous IBE, Function Privacy, Predicate Privacy, Search Pattern Privacy, Key Unlinkability.

Original Publication (with minor differences): AFRICACRYPT '14. This is the full version.

Date: received 29 May 2013, last revised 24 Mar 2014

Contact author: afonso delerue at uni lu

Available format(s): PDF | BibTeX Citation

Version: 20140324:144646 (All versions of this report)

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