The present invention relates to a system wherein each of a reservation server that makes reservations of sales and purchases, a portable terminal owned by a user who makes a reservation, and a shop terminal provided in stores where goods are sold, and a service or entertainment is provided, is connected to a communication network whereby the user makes a reservation for sales or purchase by accessing the reservation server, the reservation server encrypts contents of the sales/purchase reservation and transmits the encrypted reservation information to the aforementioned portable terminal, the user presents the transmitted encrypted reservation information to the shop terminal, visiting the shop terminal, and the shop terminal accesses the reservation server to confirm whether the presented encrypted reservation information is legitimate or not and admits the presenter of the encrypted reservation information if the reservation information is legitimate.