Cryptology ePrint Archive: Report 2006/353

Analysis and Improvements of Two Identity-Based Perfect Concurrent Signature Schemes

Zhenjie Huang and Kefei Chen and Yumin Wang

Abstract: The notion of concurrent signatures was introduced by Chen, Kudla and Paterson in their seminal paper in Eurocrypt 2004. In concurrent signature schemes, two entities can produce two signatures that are not binding, until an extra piece of information (namely the keystone) is released by one of the parties. Upon release of the keystone, both signatures become binding to their true signers concurrently. In ICICS 2005, two identity-based perfect concurrent signature schemes were proposed by Chow and Susilo. In this paper, we show that these two schemes are unfair, in which the initial signer can cheat the matching signer. We present a formal definition of ID-based concurrent signatures which redress the flaw of Chow et al.'s definition and then propose two simple but significant improvements to fix our attacks.

Category / Keywords: public-key cryptography / Concurrent signature, Identity-Based, Bilinear pairings, Cryptoanalysis, Fair exchange.

Date: received 19 Oct 2006, last revised 29 Oct 2006

Contact author: zjhuang at sjtu edu cn

Available format(s): PDF | BibTeX Citation

Version: 20061030:030809 (All versions of this report)

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