Patent ID: 8166293

Claim:
A client server distributed system configured so that a client apparatus compliant with an SIP protocol and a server apparatus compliant with the SIP protocol are connected to a network, the SIP being an abbreviation of Session Initiation Protocol, the SIP protocol operating on a UDP protocol, the UDP being an abbreviation of User Datagram Protocol, wherein the server apparatus includes: means for setting encryption information; means for creating an SIP request message containing the encryption information and notifying the client apparatus of the SIP request message; means for encrypting an SIP message to be transmitted to the client apparatus, the encrypting based on the encryption information and performed after the setting of the encryption information; means for decrypting an encrypted SIP message received from the client apparatus using the encryption information; and means for exercising a control according to a content of the decrypted SIP message, the client apparatus includes: means for setting the encryption information contained in the SIP request message received from the server apparatus; means for encrypting an SIP message to be transmitted to the server apparatus, the encrypting based on the received encryption information and performed after the encryption information is set; means for decrypting the SIP message received from the server apparatus using the encryption information; and means for exercising a control according to a content of the decrypted SIP message.