No abstract

The VPN (Virtual Private Network) technique becomes more and more popular to protect contents of messages and to achieve secure communication from incidents, such as tapping. However, it grow in usage that a VPN server is used on a sub-network in part of an office-wide network. But, a PPTP system included in Windows operating systems cannot establish nested VPN links. Moreover encrypted communication by VPN hides a user of the VPN connection. Consequently, any administrators of network systems can't find out the users of the VPN connection via firewall, moreover can't decide whether if the user is legal or not. In order to solve this problem, we developed a multi step PPTP relay system on a firewall. This system solves all the problems of our previously developed PPTP relay system (1) . The new relay system improves security by encrypting through the whole end-to-end communication and abolishing of prior registration of passwords for the next step. Furthermore, transport speed is accelerated, and the restriction of the number of steps on relay is also abolished. By these features the multi step PPTP relay system expands usability. PPTP PPTP

SUMMARYThe VPN (Virtual Private Network) technique is becoming increasingly popular as a way to protect the contents of messages and to achieve secure communications immune to such activities as eavesdropping. However, although VPN servers are increasingly used on a subnetwork in part of an officewide network, the PPTP system included in the Windows operating systems cannot establish nested VPN links. Moreover, encrypted communication by VPN hides the user of the VPN connection, and consequently the administrators of network systems cannot determine the users of the VPN connection via the firewall, or decide whether a user is legal or not. In order to solve this problem, we developed a multistep PPTP relay system on a firewall. This system solves all the problems of our previously developed PPTP relay system [1]. The new relay system improves security by end-to-end encryption of communication and eliminates the prior registration of passwords for the next step. Furthermore, the transport speed is increased and the restriction on the number of relay steps is also eliminated. These features of the multistep PPTP relay system expand its usability.