Content use management system, content use management method, and client device

摘要

A content distribution system 200 distributes a content key and content use conditions for controlling a content use in a client apparatus 110 to the client apparatus 110, via a communication channel 130, from either a multicast distribution server 122 or a unicast distribution server 123. A content distribution management server 121 determines by which distribution methods to send a content key and content use conditions of each content according to an attribute of the content (a compression format, a compression ratio, a content holder, and the like). An encrypted content distribution server 124 distributes only encrypted content whose content key and content use conditions to be distributed by the unicast, and the multicast distribution server 122 distributes encrypted content whose content key and content use conditions are superimposed by the multicast.