Patent ID: 7324822

Claim:
A transmitting device for transmitting contents for which a copyright protection is necessary, to one or more receiving devices through a network, the transmitting device comprising: a contents supply unit configured to store or generate the contents; a communication processing unit configured to select a communication mode in case of carrying out communications with receiving devices; a device authentication and key exchange processing unit configured to determine a key to be used as either a key that permits a finite number of copies or a key that prohibits copies, according to the communication mode selected by the communication processing unit, and to carry out device authentication and key exchange for the copyright protection with receiving devices; an encryption processing unit configured to encrypt the contents by using a key exchanged by the device authentication and key exchange processing unit; a network interface unit configured to transmit the contents encrypted by the encryption processing unit, to the receiving devices; and a revocation information registration unit configured to register an identification information of each receiving device to which a transmission of the contents is to be prohibited; wherein the device authentication and key exchange processing unit does not carry out the device authentication and key exchange with any receiving device whose identification information is registered in the revocation information registration unit.