Development of Internet Phone (VoIP) for Voice Security on VPN Environment

The VoIP (voice over IP) has been worldwide used and already put to practical use in many fields. However, it is needed to ensure secret of VoIP call in a special situation. It is relatively difficult to eavesdrop the commonly used PSTN in that it is connected with 1:1 circuit. However, it is difficult to ensure the secret of call on Internet because many users can connect to the Internet at the same time. Therefore, this paper suggests a new model of Internet telephone for eavesdrop prevention enabling VoIP (using SIP protocol) to use the VPN protocol and establish the probability of practical use comparing it with Internet telephone.