Perfect ambiguous optimistic fair exchange

Yang Wang, Man Ho Allen Au, Willy Susilo

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review

10 Citations (Scopus)


Protocol for fair exchange of digital signatures is essential in many applications including contract signing, electronic commerce, or even peer-to-peer file sharing. In such a protocol, two parties, Alice and Bob, would like to exchange digital signatures on some messages in a fair way. It is known that a trusted arbitrator is necessary in the realization of such a protocol. We identify that in some scenarios, it is required that prior to the completion of the protocol, no observer should be able to tell whether Alice and Bob are conducting such an exchange. Consider the following scenario in which Apple engages Intel in an exchange protocol to sign a contract that terminates their OEM agreement. The information would be of value to a third party (such as the stock broker, or other OEM companies). If the protocol transcript can serve as an evidence that such a communication is in progress, any observer of this communication, including the employees of both companies, would be tempted to capture the transcript and sell it to outsiders. We introduce a new notion called perfect ambiguous optimistic fair exchange (PAOFE), which is particularly suitable to the above scenario. PAOFE fulfils all traditional requirements of cryptographic fair exchange of digital signatures and, in addition, guarantees that the communication transcript cannot be used as a proof to convince others that the protocol is in progress. Specifically, we formalize the notion of PAOFE and present a rigorous security model in the multi-user setting under the chosen-key attack. We also present a generic construction of PAOFE from existing cryptographic primitives and prove that our proposal is secure with respect to our definition in the standard model.
Original languageEnglish
Title of host publicationInformation and Communications Security - 14th International Conference, ICICS 2012, Proceedings
Number of pages12
Publication statusPublished - 8 Nov 2012
Externally publishedYes
Event14th International Conference on Information and Communications Security, ICICS 2012 - Hong Kong, Hong Kong
Duration: 29 Oct 201231 Oct 2012

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume7618 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference14th International Conference on Information and Communications Security, ICICS 2012
Country/TerritoryHong Kong
CityHong Kong

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


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