Publication IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer SciencesVol.E90-ANo.12pp.2962-2964 Publication Date: 2007/12/01 Online ISSN: 1745-1337 DOI: 10.1093/ietfec/e90-a.12.2962 Print ISSN: 0916-8508 Type of Manuscript: LETTER Category: Information Security Keyword: fair exchange, verifiably encrypted signature, cryptanalysis,
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Summary: A fair exchange scheme is a protocol by which two parties Alice and Bob swap items or services without allowing either party to gain an advantage by quitting prematurely or otherwise misbehaving. Verifiably committed signature is a generalized and unified model for non-interactive optimistic fair exchange scheme. The state-of-the-art verifiably committed signature that enjoys the off-line, setup-free and stand-alone properties is due to Zhu and Bao [1]. In this article, we show that the Zhu-Bao's verifiably committed signature is insecure in the multi-user setting and then consider possible countermeasures.