Abstract: Usage by second content of previously distributed first content, is permitted if the proper electronic signature is incorporated into predetermined data added to the second content. A secret key and a public key are generated for the first content. The public key is added to the first content which is transmitted. When the second content seeks to refer to the first content, an electronic signature, produced by employing the secret key, is requested and incorporated into predetermined data that is added to the second content. The second content with the predetermined data is transmitted. At the receiver, the public key which was added to the first content, is used in a collating process with the received electronic signature, and when the collation succeeds, the previously received first content stored at the receiver is used in accordance with instructions received with the second content.

Abstract: The usage restriction of a first content which has already been distributed is made to efficiently function when processing in which a second content refers to the first content is performed. A secret key and a public key are generated for a first content, the public key is added to the first content to transmit the first content, and when a second content which wants to refer to the first content is generated, a signature from a administrator of the first content by the secret key generated at the time of broadcasting the first content is requested on a predetermined data added to the second content. When the signature is given, the second content to which the signed predetermined data is added is transmitted.

Abstract: The usage restriction of a first content which has already been distributed is made to efficiently function when processing in which a second content refers to the first content is performed. A secret key and a public key are generated for a first content, the public key is added to the first content to transmit the first content, and when a second content which wants to refer to the first content is generated, a signature from a administrator of the first content by the secret key generated at the time of broadcasting the first content is requested on a predetermined data added to the second content. When the signature is given, the second content to which the signed predetermined data is added is transmitted.