(1) Field of the Invention
The present invention relates to an authentication processing apparatus and an authentication processing method, and particularly to an authentication processing apparatus that performs processing for authenticating a device.
(2) Description of the Related Art
In recent years, High-Definition Multimedia Interface (HDMI) communication has been used to transmit audio and video data from a sending device such as a DVD player to a receiving device such as a television receiver. In HDMI communication, device authentication specified by the High-bandwidth Digital Content Protection (HDCP) standard is performed for copyright protection of such audio and video data.
The HDCP standard is a standard for protecting transmission of content between a sending device which encrypts and sends the content and a receiving device which receives and decrypts the content. According to the HDCP standard, the sending device authenticates the receiving device using an authentication protocol. The sending device sends the encrypted content to the receiving device based on a secret key previously shared by both devices in the device authentication. In addition, in order to keep the integrity of the HDCP-compliant system for a long time, the sending device revokes a device exposed to risk on the system. Device authentication in the HDCP standard is performed via Inter-Integrated Circuit (IIC) communication such as Display Data Channel (DDC) communication.
FIG. 1 is a block diagram which shows a structure of a conventional HDMI communication system in which device authentication is performed according to the HDCP standard. An HDMI communication system shown in FIG. 1 includes a sending device 1100 such as a DVD player and a receiving device 1200 such as a television receiver. The sending device 1100 and the receiving device 1200 are connected to each other via an HDMI cable 1300.
The sending device 1100 includes a CPU 1110 and an HDMI sending unit 1120. The CPU 1110 controls the sending device 1100 including the HDMI sending unit 1120. The HDMI sending unit 1120 is an LSI which sends audio and video data to the receiving device 1200, and includes a DDC unit 1127. The audio and video data are sent from the HDMI sending unit 1120 to the receiving device 1200 in one direction via the HDMI cable 1300.
The DDC unit 1127 performs two-way DDC communication with the receiving device 1200 via the HDMI cable 1300.
In the conventional HDMI communication system structured as mentioned above, the sending device 1100 performs authentication of the receiving device 1200 through software processing by the CPU 1110. However, since in the conventional sending device 1100, the CPU 1110 performs device authentication, it may be unable to perform high-speed authentication depending on its operational status. In the conventional system, data is sent between the CPU 1110 and the DDC unit 1127 via the DDC communication. However, in the DDC communication, since data is sent and received at a communication frequency of approximately 100 kHz, the data cannot be sent at high speed between the CPU 1110 and the DDC unit 1127.
In order to solve these problems, Japanese Laid-open Patent Application No. 2005-269135 describes a technique for executing a part of HDCP-compliant device authentication using a dedicated circuit. HDCP-compliant device authentication is the processing specified by the HDCP standard, and the processing can be performed using a circuit composed of hardware.