| 摘要 |
A conditional access overlay system utilizing partial encryption without requiring additional program identifiers. The conditional access overlay system generates duplicate critical packets for separate encryption that are sent using the same packet identifier. The rest of the content stream is sent in the clear. However, these duplicated packets are sent without incrementing a continuity counter relative to one another. The overlay packets with non-incremented continuity counter are sent as the second packet immediately following the original critical packet. At the receivers, the incumbent set-top will use the first of the two encrypted packets while the overlay set-top is programmed to use the second of the two encrypted packets. Therefore, methods for verifying alignment of associated packets may be used to distinguish between multiple encryption methods in conditional access overlay systems. |
