US Patent 8346668 Electronic money system and electronic money transaction method

An electronic money system is directed to avoid unauthorized use of certificate-type electronic money. The electronic money system is provided with a management server, a verification sever, a remittance terminal, and a receptor terminal. In response to a request from the remittance terminal, the management server issues an inactive electronic certificate including a certificate ID and notifies the verification server of the certificate ID. The remittance terminal gives a group signature to the inactive electronic certificate to generate an active electronic certificate. The reception terminal verifies the active electronic certificate obtained from the remittance terminal on the basis of the group signature. The verification server matches the certificate ID notified from the management server with the certificate ID included in the active electronic certificate verified by the reception terminal to verify availability of the active electronic certificate.