Optimistic Fair Exchange in a Multi-user Setting

: 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 oneway functions in the random oracle model and trapdoor one-way permutations in the standard model. Finally, we revisit two well-known metho...

• Type: Conference
• Year: 2007
• Where: PKC
• Authors: Yevgeniy Dodis, Pil Joong Lee, Dae Hyun Yum
• Keywords: Cryptography, Multi-user Setting, Optimistic Fair Exchange, PKC 2007, Single-user Setting