Control of usage of contents in digital broadcasts

摘要

A method of transmitting a content to a reception side includes the steps of encrypting the content by use of a scramble key that varies with time, encrypting scramble-key-associated information that includes at least the scramble key and usage-control information, the usage-control information indicative of usage of the content on the reception side, and transmitting the encrypted content and the encrypted scramble-key-associated information to the reception side.