ID‐Based Optimistic Fair Exchange Scheme Based on RSA

Fairness of exchange is a significant property for secure online transactions, and a fair exchange scheme is a useful tool for ensuring the fairness of exchanges conducted over networks. In this paper, we propose an ID‐based optimistic fair exchange scheme based on the RSA function, one which is designed by combining a well‐known RSA‐based signature scheme and the (naive) RSA function. Note that the main contribution of this paper is to give the first provably secure ID‐based fair exchange scheme based on the RSA function, whose security can be proved under fully formalized security models. Our scheme has the following additional strongpoints. The scheme is setup‐free; hence, there is no registration step between a user and an arbitrator. Moreover, the proposed scheme is designed in an ID‐based setting; thus, it is possible to eliminate the need for certificates and avoid some related problems.