Abstract:
There is provided a content distribution system using the Internet employing the multi-cast method. Information on each sub license of a main body of ECM (Entitlement Control Message) includes a license ID which is sub license identification information, type information indicating whether the sub license is for preview or main view, and a location indicating the storage position (the number of bytes from the head of the ECM main body) in the license section of the sub license. The license section contains the sub license.