System and method for electronic bidding

Abstract

In an electronic bidding system and method, it is unnecessary to disclose to bidders a list of public keys matched to bid prices, and in which price secrecy may be proved. In a function of encryption of a bidding device, a public key is generated using a bid price and an IBE public key, based on an ID-Based Encryption (IBE) system having a bid value as an ID. IBE public key is obtained on combining a plurality of partial public keys matched to partial secret keys generated by a plural number of partial bid opening devices based on a combination condition enabling group decryption. A preset message for bidding is then encrypted. In a function of decryption of a bid opening device, a number of partial bid opening devices, which is in keeping with a satisfying number of the group decryption, perform calculations for decryption for winning bid value candidates, beginning from such candidate, the allowable bid value closest to the bid closing condition. Decrypted data obtained on combining the resulting output partial bid opening data are collated to the message for bidding to decide on winning bid value.