Cryptology ePrint Archive: Report 2013/497

Improvement of Camenisch-Neven-Shelat Oblivious Transfer Scheme

Zhengjun Cao and Hanyue Cao

Abstract: In 2007, Camenisch, Neven and Shelat proposed an adaptive oblivious transfer (OT) in which a sender has $N$ messages, of which a receiver can adaptively choose to receive $k$ one-after-the-other. In this paper, we show that the scheme has a drawback that the sender can only serve a single receiver only once. The drawback results from the deterministic encryption used. To fix it, we suggest to replace the deterministic encryption with a probabilistic encryption. The OT scheme adopts the paradigm of ``encryption and proof of knowledge" in order to force the sender to keep the consistency of the transferred messages. We remark that the paradigm is unnecessary. In most reasonable applications of OT, the transferred messages must be recognizable for the receiver or the sender is willing to disclose some messages to the receiver. This property has been explicitly specified in the earlier works by Rabin, Even, Goldreich and Lempel.

Category / Keywords: cryptographic protocols / Oblivious transfer, deterministic encryption, probabilistic encryption, recognizable message

Date: received 13 Aug 2013

Contact author: caozhj at shu edu cn

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Version: 20130815:072552 (All versions of this report)

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