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Revisiting optimistic fair exchange based on ring signatures

Journal Article


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Abstract


  • Optimistic fair exchange (OFE) is a kind of protocol

    that solves the fair exchange problem with the help of a trusted

    third party, usually referred to as an arbitrator. Participation of

    the arbitrator is required only when there is a dispute amongst

    the exchanging parties. Thus, the majority of the executions of

    the exchange does not involve the arbitrator and hence the term

    optimistic. The passive nature of the arbitrator makes optimistic

    fair exchange a desirable tool in applications such as contract

    signing and electronic commerce. The highest level of security of

    optimistic fair exchange in the literature is the multi-user security

    in the chosen-key model, proposed by Huang, Yang, Wong and

    Susilo in CT-RSA 2008. They showed that an efficient optimistic

    fair exchange scheme secure in this sense can be constructed

    generically from a conventional digital signature and a two-party

    ring signature. In particular, the underlying ring signature is

    required to be unforgeable under an adaptive attack, against a

    static adversary in the 2-user setting.

    In this paper we propose a new security model for two-party

    ring signatures called unforgeability against restricted adaptive

    attacks and demonstrate that our new model is strictly weaker

    than the model of unforgeable under an adaptive attack, against

    a static adversary in the 2-user setting. We make an observation

    that two-party ring signatures secure in this weaker model will

    suffice to guarantee the security of the resulting OFE scheme

    following the aforementioned generic construction. Based on this

    observation, more efficient OFE schemes secure in the standard

    model can be constructed. Specifically, we prove that the wellknown

    Bender, Katz and Morselli’s 2-user ring signature is

    secure in our weakened model. Based on this two-party ring

    signature, we construct an OFE secure in the chosen-key model

    offering multi-user security in the standard model under the

    Computational Diffie-Hellman assumption. The assumption is

    arguably weaker than those used in all existing constructions,

    which rely on the random oracle model, decisional assumptions

    or the Strong Diffie-Hellman assumptions. It is also worth noting

    that our scheme is the most efficient one in the standard model,

    and offers comparable efficiency against those secure under the

    random oracle model.

UOW Authors


  •   Wang, Yang (external author)
  •   Au, Man Ho Allen (external author)
  •   Susilo, Willy

Publication Date


  • 2014

Citation


  • Wang, Y., Au, M. Ho Allen. & Susilo, W. (2014). Revisiting optimistic fair exchange based on ring signatures. IEEE Transactions on Information Forensics and Security, 9 (11), 1883-1892.

Scopus Eid


  • 2-s2.0-84908067008

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=5117&context=eispapers

Ro Metadata Url


  • http://ro.uow.edu.au/eispapers/4096

Number Of Pages


  • 9

Start Page


  • 1883

End Page


  • 1892

Volume


  • 9

Issue


  • 11

Abstract


  • Optimistic fair exchange (OFE) is a kind of protocol

    that solves the fair exchange problem with the help of a trusted

    third party, usually referred to as an arbitrator. Participation of

    the arbitrator is required only when there is a dispute amongst

    the exchanging parties. Thus, the majority of the executions of

    the exchange does not involve the arbitrator and hence the term

    optimistic. The passive nature of the arbitrator makes optimistic

    fair exchange a desirable tool in applications such as contract

    signing and electronic commerce. The highest level of security of

    optimistic fair exchange in the literature is the multi-user security

    in the chosen-key model, proposed by Huang, Yang, Wong and

    Susilo in CT-RSA 2008. They showed that an efficient optimistic

    fair exchange scheme secure in this sense can be constructed

    generically from a conventional digital signature and a two-party

    ring signature. In particular, the underlying ring signature is

    required to be unforgeable under an adaptive attack, against a

    static adversary in the 2-user setting.

    In this paper we propose a new security model for two-party

    ring signatures called unforgeability against restricted adaptive

    attacks and demonstrate that our new model is strictly weaker

    than the model of unforgeable under an adaptive attack, against

    a static adversary in the 2-user setting. We make an observation

    that two-party ring signatures secure in this weaker model will

    suffice to guarantee the security of the resulting OFE scheme

    following the aforementioned generic construction. Based on this

    observation, more efficient OFE schemes secure in the standard

    model can be constructed. Specifically, we prove that the wellknown

    Bender, Katz and Morselli’s 2-user ring signature is

    secure in our weakened model. Based on this two-party ring

    signature, we construct an OFE secure in the chosen-key model

    offering multi-user security in the standard model under the

    Computational Diffie-Hellman assumption. The assumption is

    arguably weaker than those used in all existing constructions,

    which rely on the random oracle model, decisional assumptions

    or the Strong Diffie-Hellman assumptions. It is also worth noting

    that our scheme is the most efficient one in the standard model,

    and offers comparable efficiency against those secure under the

    random oracle model.

UOW Authors


  •   Wang, Yang (external author)
  •   Au, Man Ho Allen (external author)
  •   Susilo, Willy

Publication Date


  • 2014

Citation


  • Wang, Y., Au, M. Ho Allen. & Susilo, W. (2014). Revisiting optimistic fair exchange based on ring signatures. IEEE Transactions on Information Forensics and Security, 9 (11), 1883-1892.

Scopus Eid


  • 2-s2.0-84908067008

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=5117&context=eispapers

Ro Metadata Url


  • http://ro.uow.edu.au/eispapers/4096

Number Of Pages


  • 9

Start Page


  • 1883

End Page


  • 1892

Volume


  • 9

Issue


  • 11