In public auction, all bid values are published, but each bidder participates in auction protocol in anonymous way. Recently, Omote and Miyaji [OM01] proposed a new model of public auction in which any bidder can participate in plural rounds of auction with one-time registration. They have introduced two managers, registration manager (RM) and auction manager (AM), and have used efficient tools such as bulletin board and signature of knowledge [CS97].In this scheme, even if a bidder is identified as a winner in a round, he can participate in next rounds of auction maintaining anonymity for RM, AM, and any bidder. But a problem of this protocol is that the identity of winner cannot be published. In the winner announcement stage, RM informs the vendor of winner’s identity secretly. Therefore RM’s final role cannot be verified, and AM and any participating bidder can not be sure of the validity of auction.
In this paper, we propose a new public auction scheme which can solve this problem. In the proposed scheme, both RM and AM execute randomization operation in round setup process which makes the publication of winner’s identity be possible while keeping anonymity of winner in next rounds of auction. Moreover, AM provides ticket identifier based on Diffie-Hellman key agreement which is recognized only by the bidder. Our scheme provides real anonymity in plural rounds of auction with one-time registration in a verifiable way.