SOURCE AUTHENTICATION OF DOWNLOAD INFORMATION IN CONDITIONAL ACCESS SYSTEM

摘要

PROBLEM TO BE SOLVED: To obtain a cable television system which provides conditional access to service. SOLUTION: The cable television system includes a headend from which service "instances" or programs are broadcast and a plurality of set top units for receiving the instances and selectively decrypting the instances for display to system subscribers. The service instances are encrypted by using public and/or private keys provided by service providers or central authorization agents. Keys used by the set tops for selective decryption may also be public or private in nature. Such keys may be reassigned at different times, and a cable television system in which piracy concerns are minimized, is provided. COPYRIGHT: (C)2005,JPO&NCIPI