Encryption and content control in a digital broadcast system

摘要

A selective encryption encoder has a packet identifier that identifies packets of a specified packet type forming a part of a program. A packet duplicator duplicates the identified packets to produce first and second sets of the identified packets. A PMT (program map table) inserter generates temporary identifying information that identifies the first and second sets of identified packets inserts the temporary identifying information as user private data in a program map table (PMT) forming a part of the transport program specific information (PSI). The data are then sent to and received from a primary encryption encoder to encrypt the first set of identified packets under a first encryption method. A secondary encrypter encrypts the second set of identified packets under a second encryption method. The PSI is then modified at a PSI modifier to remove the temporary identifying information and to correctly associate the first and second sets of identified packets and the unencrypted packets with the program.