Patent ID: 7036021

Claim:
An image display device that has an authentication/decryption unit for authenticating and decrypting encrypted video signals and a display for displaying video signals thereon, said image display device comprising: open-condition detecting means for detecting whether a cabinet of said image display device is opened; storing means for storing one of a first flag indicating that an authentication operation of said authentication/decryption unit is enabled and a second flag indicating that the authentication operation of said authentication/decryption unit is disabled; flag writing means for writing said second flag into said storing means when said open-condition detecting means detects that said cabinet is opened; enabling/disabling control means for controlling enabling/disabling of the authentication operation of said authentication/decryption unit according to the flag stored in said storing means; first display control means for putting said display in a first state by displaying the video signals decrypted from the encrypted video signals when the flag stored in said storing means is the first flag; and second display control means for putting said display in a second state, which is different from the first state, when the flag stored in said storing means is the second flag.