False-name-proof Multi-unit Auction Protocol Utilizing Greedy Allocation based on Approximate Evaluation Values

This paper presents the new false-name-proof multi-unit auction protocol called Greedy ALlocation (GAL) protocol. Although Internet auctions have been growing very rapidly, the possibility of a new type of cheating called false-name bids has been identified.False-name bids are bids made under fictitious names, e.g., multiple e-mail addresses. A protocol called the Iterative Reducing (IR) protocol has been developed for multi-unit auctions and proven to be false-name-proof, i.e., using false-name bids is useless. For Internet auction protocols, being false-name-proof is important since identifying each participant is virtually impossible. One shortcoming of the IR protocol is that it requires the auctioneer to carefully pre-determine a reservation price for one unit. Our newly developed GAL protocol is easier to use than the IR, since the auctioneer does not need to set a reservation price. The results of evaluation show that the GAL protocol obtains a social surplus that is very close to Pareto efficient. Furthermore, the obtained social surplus and seller's revenue are much greater than with the IR protocol even if the reservation price is set optimally.