International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Optimistic Fair Exchange in a Multi-user Setting

Authors:
Yevgeniy Dodis
Pil Joong Lee
Dae Hyun Yum
Download:
URL: http://eprint.iacr.org/2007/182
Search ePrint
Search Google
Abstract: 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.
BibTeX
@misc{eprint-2007-13464,
  title={Optimistic Fair Exchange in a Multi-user Setting},
  booktitle={IACR Eprint archive},
  keywords={cryptographic protocols / fair exchange},
  url={http://eprint.iacr.org/2007/182},
  note={A preliminary version appeared in PKC 2007. dhyum@postech.ac.kr 13648 received 15 May 2007},
  author={Yevgeniy Dodis and Pil Joong Lee and Dae Hyun Yum},
  year=2007
}