Abstract: There are provided an apparatus and method for transmitting data in a network system using network address translation. The method for transmitting data includes the steps of receiving a global network address corresponding to a local network address from a router using network address translation; encoding data using the global network address; and transmitting the encoded data to an external host on the global network via the router. Since the network address to be translated through the network address translation can be anticipated and substituted in real time during the transmission of the data, a variety of security services can be provided without significant modifications to the existing system, and accordingly, it is anticipated that the Internet protocol version 6 can be increasingly used.

Abstract: A method for controlling an Internet information security system of a sender, for packet security in an IP level, is provided. It is determined whether to select security services of packets by referring to security policy database and security association database. Security association is negotiated with a key exchange server of a receiver. The negotiated security association is stored in a key management server. A security policy related with the security association is linked. A packet is sent by using the linked security policy and the security association.