Patent ID: 7965846

Claim:
A client-server type distributed system corresponding to the SIP (Session Initiation Protocol) connected to the Internet/intranet/LAN (Local Area Network), wherein when authentication between SIP-protocol-coping client apparatuses and an SIP-protocol-coping server apparatus is completed, and an RTP (Real-time Transport Protocol) connection between the client apparatuses is an SIP call connection through the server apparatus, the server apparatus comprises: means for setting two or more types of RTP encrypting information used in an RTP packet transmission/reception to one unit of the client apparatuses, setting at least one type of RTP encrypting information used in an RTP packet/transmission/receipt to an other unit of the client apparatuses, and managing the RTP encrypting information as the encrypting capability information of the client apparatuses; means for determining one type of RTP encrypting information used between the client apparatuses each time an RTP communication occurs between the client apparatuses; and means for notifying the client apparatuses of the RTP encrypting information, and each of the client apparatuses comprises: means for receiving and setting RTP encrypting information used in an RTP packet transmission/reception to other client apparatus; and a function for encrypting an RTP packet and transmitting the RTP packet to confronting client apparatuses in the P2P (Peer-to-Peer) between the client apparatuses in the RTP communication according to the RTP encrypting information received from the server apparatus as well as for receiving the encrypted RTP packet from the confronting client apparatuses and decrypting the encrypted RTP.