Method for partially encrypting program data
View Patent ↗A cable television system provides conditional access to services. 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 partially-encrypted 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, and such keys may be reassigned at different times to provide a cable television system in which piracy concerns are minimized.
1. A method for providing a plurality of programs in a conditional access system, the method comprising the steps of:
using a packet identifier to select for encryption a portion of each of a plurality of digital bit streams from a multimedia transport stream according to a plurality of at least a first and a second encryption methods;
encrypting the selected portion of each of the plurality of digital bit streams prior to combining the encrypted portion and the unencrypted portion with the transport stream; and
transmitting the combined stream.
2. The method of claim 1 , wherein each of the plurality of digital bit streams includes a packet identifier, and wherein using a packet identifier to select for encryption selects a portion of each of the plurality of digital bit streams by identifying a predetermined packet identifier.
3. The method of claim 1 , wherein each of the plurality of digital bit streams includes a packet identifier, and wherein using a packet identifier to select for encryption selects the plurality of digital bit streams by identifying a plurality of predetermined packet identifiers.
4. The method of claim 3 , wherein the selected plurality of digital bit streams are programs.
5. The method of claim 3 , wherein the selected plurality of digital bit streams are elementary digital bit streams.
6. The method of claim 3 , wherein a portion of the selected plurality of digital bit streams is encrypted according to the packet identifier associated with each of the plurality of digital bit streams.
7. The method of claim 6 , wherein the packet identifier is indicative of each of the plurality of digital bit streams being one of a video stream, an audio stream, and a data stream.
8. The method of claim 7 , wherein the encrypted portion includes at least one of the plurality of digital bit streams associated with the video stream.
9. The method of claim 7 , wherein the encrypted portion includes at least one of the plurality of digital bit streams associated with the audio stream.
10. The method of claim 7 , wherein the encrypted portion includes at least one of the plurality of digital bit streams associated with the data stream.
11. The method of claim 7 , wherein the encrypted portion includes at least one of the plurality of digital bit streams associated with at least one of the video stream, the audio stream, and the data stream.
12. A method for providing a plurality of programs in a conditional access system, the method comprising the steps of:
using a packet identifier to select for encryption a portion of a plurality of elementary bit streams from a plurality of programs according to a plurality of at least a first and a second encryption methods;
encrypting the selected portion of each of the plurality of elementary bit streams from said plurality of programs prior to combining the encryption portion and the remaining portion of the streams with said plurality of programs to provide a partially-encrypted stream; and
transmitting the partially-encrypted stream.
13. The method of claim 12 , wherein each of the plurality of elementary bit streams includes a plurality of packets, each packet having a packet header.
14. The method of claim 13 , wherein the packet header includes a packet identifier identifying the packet, wherein the packet identifier is indicative of one of a video stream, an audio stream, and a data stream.
15. The method of claim 14 , wherein the encrypted portion includes at least one of the plurality of packets associated with the video stream.
16. The method of claim 14 , wherein the encrypted portion includes at least one of the plurality of packets associated with the audio stream.
17. The method of claim 14 , wherein the encrypted portion includes at least one of the plurality of packets associated with the data stream.
18. The method of claim 14 , wherein the encrypted portion includes at least one of the plurality of packets associated with at least one of the video stream, the audio stream, and the data stream.