Patent ID: 8286224

Claim:
An authentication device for authenticating a terminal device according to a certain authentication protocol with respect to both an IEEE 802.1X protocol that is defined in a data link layer in a protocol stack and a higher layer protocol that is defined in a higher layer than a UDP(User Datagram Protocol)/IP(Internet Protocol) layer or a TCP(Transmission Control Protocol)/IP(Internet Protocol) layer in the protocol stack, the certain authentication protocol being operable on both of the IEEE 802.1X and the higher layer protocols, comprising: a first acquisition unit configured to acquire a first message required for the terminal device to be subject to authentication with respect to the IEEE 802.1X protocol, from the terminal device; a sending-back unit configured to send-back a success message to the terminal device to notify the terminal that the authentication with respect to the IEEE 802.1X protocol is successful without performing IEEE 802.1X protocol authentication when a predetermined authentication identifier is contained in the first message; a data link establishing unit configured to establish a data link of the data link layer with the terminal device to which the success message has been sent-back; a filtering unit configured to perform filtering on packets of the UDP/IP or the TCP/IP received from the terminal device through the data link; a first filter setting unit configured to set the filtering unit so as to pass a first packet required for the terminal device to be subjected to authentication with respect to the higher layer protocol from among the packets from the terminal device and to block second packets different from the first packet, when the authentication identifier is contained in the first message; a second acquisition unit configured to acquire a second message carried by the first packet from the terminal device, the second message being required for authentication with respect to the higher layer protocol; an authentication unit configured to authenticate the terminal device from which the second message is acquired, with respect to the higher layer protocol; and a second filter setting unit configured to set the filtering unit so as to pass second packets from the terminal device when the authentication with respect to the higher layer protocol is successful.