Object To provide a technique for authenticating a communication partner using an electronic certificate containing personal information. Solving Means When a client apparatus receives a request for an electronic certificate from a server apparatus, the server apparatus reads a client certificate containing personal information and a server public key of the server apparatus from a storage unit and encrypts the client certificate using the server public key. The client apparatus also creates a temporary electronic certificate by setting, in a basic field of an electronic certificate, a predetermined item indicating that the electronic certificate is a temporary electronic certificate and by setting the client certificate having been encrypted in an extension field of the electronic certificate. Then, the client apparatus sends the temporary electronic certificate to the server apparatus.