There is provided a communication device in which a network access authenticating unit executes a network access authentication process with an authentication server to establish a connection to a network, the authentication process including generation of information shared with the authentication server, a communication unit receives an authentication result message from the authentication server when succeeding in the network access authentication process, the authentication result message containing an authentication result indicating success in the network access authentication process and an encrypted network key; a key transport key generating unit generates a key transport key by use of the information generated in the network access authentication process; and a network key acquiring unit acquires a network key by decrypting the encrypted network key contained in the authentication result message with the key transport key, the communication unit encrypts data with the network key and transmits encrypted data to the network.