When encryption information including an encryption rule, an encryption range, and an encryption key is input to a server apparatus from a local maintenance console in advance, the server apparatus stores the encryption information in an encryption information setting unit, creates an SIP request message including the encryption information, and transmits the SIP request message to a client apparatus. The client apparatus receives the SIP request message including the encryption information. If confirming normality of the encryption information, the client apparatus sets the encryption information therein. After completion of a setting of the encryption information, the client apparatus transmits a notification of the completion of the setting of the encryption information to the server apparatus. Upon receiving the notification of the completion of the setting of the encryption information, the server apparatus acknowledges the completion of the setting of the encryption information,sets the encryption information therein, transmits the notification of the completion of the setting of the encryption information to the local maintenance console, and causes the local maintenance console to display the completion of the setting of the encryption information.