Anonymous Bidding Protocols Using an Anonymous Undeniable Signature
Toru Nakanishi, Toru Fujiwara, Hajime Watanabe · NAIST Digital Library (Nara Institute of Science and Technology) · 1999
Anonymous bidding protocols using an anonymous undeniable signature scheme without assuming the existence of any reliable center are proposed. The anonymity of a bidding protocol means that the participation of anyone to the bidding except for a successful bidder is kept secret. For simplicity, assume that the bidder who bids the lowest price is chosen as the successful bidder. Then we point out that fairness of an anonymous bidding would be violated if it is possible for the bidder who bids the lowest price not to reveal his name and to withdraw the bid. Thus the key to construct the anonymous bidding protocol is to give a method for identifying the bidder who bids the lowest price but does not reveal his name. An anonymous bidding protocol proposed so far solves this problem by assuming the existence of reliable centers. Instead of assuming the existence of any reliable center, an anonymous undeniable signature scheme is used in this paper. The anonymity of a signature scheme means that anyone cannot distinguish a signature of a signer from that of another. The validity of a signature in the anonymous undeniable signature scheme is verified by an interactive manner. The true signer cannot repudiate his signature and the others can repudiate it. Thus by communicating with all candidates of the signer, it is possible to identify the true signer. In this paper, it is proved that the anonymous undeniable signature scheme can be constructed. A basic bidding protocol using the anonymous undeniable signature scheme is presented first, where the manager of the bidding has to communicate with every user in the network to identify illegal bidders, only when the existence of them is detected. By grouping users, we construct a modified protocol where the manager has only to communicate with every user in some specified groups to identify illegal bidders.