Cryptology ePrint Archive: Report 2012/469

Perfect Keyword Privacy in PEKS Systems

Mototsugu Nishioka

Abstract: This paper presents a new security notion, called \emph{perfect keyword privacy (PKP)}, for non-interactive public-key encryption with keyword search (PEKS) \cite{bcop04}. Although the conventional security notion for PEKS guarantees that a searchable ciphertext leaks no information about keywords, it gives no guarantee concerning leakage of a keyword from the trapdoor. PKP is a notion for overcoming this fatal deficiency. Since the trapdoor has verification functionality, the popular concept of ``indistinguishability'' is inadequate for capturing the notion of keyword privacy from the trapdoor. Hence, our formalization of PKP depends on the idea of formalizing a perfectly one-way hash function \cite{can97,cmr98}. We also present \emph{IND-PKP security} as a useful notion for showing that a given PEKS scheme has PKP. Furthermore, we present PKP+ and IND-PKP+ as enhanced notions of PKP and IND-PKP, respectively. Finally, we present several instances of an IND-PKP or IND-PKP+ secure PEKS scheme, in either the random oracle model or the standard model.

Category / Keywords: public-key cryptography / PEKS, perfectly one-way hash function

Publication Info: Full version of ProvSec 2012 paper

Date: received 15 Aug 2012

Contact author: mototsugu nishioka rc at hitachi com

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Version: 20120818:034932 (All versions of this report)

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