Abstract: There are provided a network settling card and a network settling program, which can perform a settling procedure on a commodity selected by a user, in a shopping system through a network or in an actual shop, even if the card information and the personal information of the user and so on are not notified, as well as an authentication server, and a shopping system and a settling method. The network settling card includes an authentication processing unit for performing authentication using an authentication key created on the basis of the information of a card to be used in a settling procedure. The authentication processing unit performs the settling procedure on the commodity selected by the user by creating a one-time ID by an authentication key, by acquiring a one-time ID created by an authentication server for authenticating the one-time ID, and by authenticating the authentication server by the authentication key.

Abstract: A method of mutual authentication between a server and a plurality of clients, including: (a) generating, by a client, a first client random number and a first client one time ID based on first and second values; (b) sending the first client one time ID and an encrypted version of the first client random number to the server by the client; (c) generating, by the server, a first server random number and a first server ID based on the first client random number and the first value; (d) sending, by the server, the first server one time ID and an encrypted version of the first server random number to the client by the server; (e) generating, by the client, a second client random number and a second client one time ID based on said first server and first client random numbers; (f) sending, by the client, the second client one time ID and an encrypted version of the second client random number to the server by the client; (g) generating, by the server, a second server random number and a second server one time ID b

Abstract: An objective of the present invention is to obtain a mutual authentication method in which mutual authentication is carried out securely and conveniently. In order to achieve the above objective, in the mutual authentication process, a private key K0, being an initial value, is stored in a client and a server (Pc0, Ps0). The client generates a random number R, calculates secret data C and authentication data A, and transmits the data items to the server (Pc1). The server receives the authentication data A and the secret data C from the client, and generates a random number Q, calculates secret data S, and authentication data B and returns the data items, as well as updating the private key K0 with a private key K1 (Ps1). The client receives from the server the authentication data B and the secret data S, generates the random number R, calculates secret data C2, authentication data A2, and returns the data items to the server, and updates the private key K0 with the private key K1(Pc2).