Patent ID: 7640597

Claim:
An image display device comprising: an authentication/decryption unit configured to authenticate and decrypt encrypted video signals; a display configured to display video signals thereon; an open-condition detector configured to detect whether a cabinet of said image display device is opened; a memory configured to store 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; a flag writer configured to write said second flag into said memory when said open-condition detector detects that said cabinet is opened; an enabling/disabling controller configured to control enabling/disabling of the authentication operation of said authentication/decryption unit according to the flag stored in said memory; and a display controller configured to put said display in a first state by displaying the video signals decrypted from the encrypted video signals when the flag stored in said memory is the first flag, and to put said display in a second state, which is different from the first state, when the flag stored in said memory is the second flag.