Network system and method for networking

A first terminal, a second terminal and the pre When a specified time elapses, and the transport key are invalidated including networking auxiliary device providing the first terminal or the second terminal, the first terminal is encrypted network key with the transmission It said first and sent to the second terminal, the second terminal can store the decryption key, the network key, transmitting the encrypted key to the transport, and easily commissioning the terminal is a network system in which the security can be improved is provided.