Authentication method, notification method, source device, and sink device

A method for use in a sink device, the method comprising:

• receiving a random number from the source device through a High Definition Multimedia Interface-Consumer Electronics Control (HDMI-CEC) bus;
• encrypting the received random number with a first secret key corresponding to the sink device;
• and
• transmitting first signature information and capability information to the source device through the HDMI-CEC bus, the first signature information being obtained by encrypting the random number, the capability information storing therein information about a display capability of the sink device.

A method for use in an AV system including a sink device and a source device, the method comprising:

• the source device acquiring a random number;
• the source device transmitting the acquired random number to the sink device through a High Definition Multimedia Interface-Consumer Electronics Control (HDMI-CEC) bus;
• the sink device receiving the random number from the source device though the HDMI-CEC bus;
• the sink device encrypting the received random number with a first secret key corresponding to the sink device;
• the sink device transmitting first signature information and capability information to the source device though the HDMI-CEC bus, the first signature information being obtained by encrypting the random number, the capability information storing therein information about a display capability of the sink device;
• the source device receiving the first signature information and the capability information from the sink device though the HDMI-CEC bus, the first signature information being information in which the random number is encrypted with the first secret key correlated with the sink device, the capability information being information about the display capability of the sink device;
• the source device acquiring a result of a first determination whether first decrypted information is compatible with the transmitted random number, the first decrypted information being obtained by decrypting the received first signature information with a first public key correlated with the sink device;
• when the result of the first determination is that the first decrypted information is compatible with the transmitted random number, the source device determining that the received capability information is correct information;
• and
• the source device outputting video corresponding to the capability information determined to be correct information to the sink device.

A source device comprising:

• a first acquisitioner that acquires a random number;
• a transmitter that transmits the random number acquired with the first acquisitioner to a sink device through a High Definition Multimedia Interface-Consumer Electronics Control (HDMI-CEC) bus;
• a receiver that receives first signature information and capability information from the sink device through the HDMI-CEC bus, the first signature information being information in which the random number is encrypted with a first secret key correlated with the sink device, the capability information being information about a display capability of the sink device;
• a second acquisitioner that acquires a result of a first determination whether first decrypted information is compatible with the random number transmitted from the transmitter, the first decrypted information being obtained by decrypting the first signature information received using the receiver with a first public key correlated with the sink device;
• a determinator that determines that the capability information received using the receiver is correct information when the result of the first determination is that the first decrypted information is compatible with the random number transmitted from the transmitter;
• and
• an output that outputs video corresponding to the capability information determined to be correct information to the sink device.

A sink device comprising:

• a receiver that receives a random number from a source device through a High Definition Multimedia Interface-Consumer Electronics Control (HDMI-CEC) bus;
• an encryptor that encrypts the random number received using the receiver with a first secret key included in the sink device;
• and
• a transmitter that transmits first signature information and capability information to the source device by the HDMI-CEC bus, the first signature information being obtained such that the encryptor encrypts the random number, the capability information storing therein information about a display capability of the sink device.