Patent ID: 7359511

Claim:
A transmission system comprising: a video transmission device operable to encrypt and transmit frame information that includes digital video information while providing one or more blanking intervals during the frame information; and a video display device operable to receive and decrypt the encrypted frame information, extract the digital video information from the decrypted frame information, and display the extracted video information, wherein the video transmission device is operable to multiplex digital audio information with the frame information in the one or more blanking intervals, encrypt the multiplexed frame information with which the digital audio information has been multiplexed, and transmit the encrypted frame information, the video display device is operable to receive the encrypted frame information, decrypt the received encrypted frame information to generate frame information, extract the digital audio information from the one or more blanking intervals provided in the generated frame information, and convert the extracted digital audio information to an audio signal, the digital video information includes a plurality of pieces of line video information that correspond respectively to lines in a frame, and the digital audio information includes a plurality of pieces of line audio information that correspond respectively to the lines in the frame, the video transmission device, for each line in the frame, is operable to set an initial value for audio, encrypt a corresponding piece of line audio information using the set initial value for audio with an encryption method, then set an initial value for video to have a same value as the initial value for audio, and encrypt a corresponding piece of line video information using the set initial value for video with the encryption method, and the video display device, for each line in the frame is operable to set an initial value for audio, decrypt a corresponding piece of line audio information using the set initial value for audio with a decryption method, then set an initial value for video to have a same value as the initial value for audio, and decrypt a corresponding piece of line video information using the set initial value for video with the decryption method.