2007 | OriginalPaper | Buchkapitel
Optimistic Fair Exchange in a Multi-user Setting
verfasst von : Yevgeniy Dodis, Pil Joong Lee, Dae Hyun Yum
Erschienen in: Public Key Cryptography – PKC 2007
Verlag: Springer Berlin Heidelberg
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This paper addresses the security of
optimistic fair exchange
in a
multi-user
setting. While the security of public key encryption and public key signature schemes in a single-user setting guarantees the security in a multi-user setting, we show that the situation is different in the optimistic fair exchange. First, we show how to break, in the multi-user setting, an optimistic fair exchange scheme provably secure in the single-user setting. This example separates the security of optimistic fair exchange between the single-user setting and the multi-user setting. We then define the formal security model of optimistic fair exchange in the multi-user setting, which is the first complete security model of optimistic fair exchange in the multi-user setting. We prove the existence of a generic construction meeting our multi-user security based on one-way functions in the random oracle model and trapdoor one-way permutations in the standard model. Finally, we revisit two well-known methodologies of optimistic fair exchange, which are based on the verifiably encrypted signature and the sequential two-party multisignature, respectively. Our result shows that these paradigms remain valid in the multi-user setting.