International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 25 June 2013

Tal Malkin, Isamu Teranishi, Moti Yung
ePrint Report ePrint Report
Semantic-security of individual bits under a ciphertext are fundamental notion in modern cryptography. In this work we present the first results about this fundamental problem for Order-Preserving Encryption (OPE): ``what plaintext information can be semantically hidden by OPE encryptions?\'\' While OPE has gained much attention in recent years due to its usefulness in secure databases, any partial-plaintext indistinguishability (semantic security) result for it was open. Here, we propose a new indistinguishability-based security notion for OPE, which can ensure \\emph{secrecy of lower bits of a plaintext} (under essentially a random ciphertext probing setting). We then propose a new scheme satisfying this security notion (while earlier schemes do not satisfy it!). We note that the known security notions tell us nothing about the above partial- plaintext indistinguishability because they are limited to being one-way-based. In addition, we show that our security notion with specific parameters implies the known security notion called WOW, and further, our scheme achieves WOW with better parameters than earlier schemes.

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