System, method, and medium for broadcasting service contents

摘要

A Ca server 13 generates and encrypts a work key (Kw) and delivers the key to receiving terminals. The CA server further updates scramble key (Ks) at a predetermined interval and delivers the key to the terminals. A contents server 14 encrypts service contents using the Kw and the Ks to deliver the contents toward an IP address for the group. A delivering router 15 receives the contents and delivers the content to the receiving terminals based on the IP address. The receiving terminals, when receives the encrypted contents, decode the contents using the Kw and the Ks and replace the IP address with its own IP address.