A PARTIAL DUAL-ENCRYPTED STREAM UTILIZING PROGRAM MAP TABLES

摘要

The present invention is suitable for use in a partial dual encrypted system. The present invention allows for two different decryption devices (e.g., an incumbent, or first, set-top and an overlay, or second, set-top) to be located in a single system having an incumbent encryption scheme and a second encryption scheme. Each set-top is designed to decrypt the first or second proprietary encryption schemes, respectively. In accordance with the present invention, the second set-top utilizes a novel program map table to ensure that the second set-top chooses correct elemenentary streams in the partial dual-encrypted stream (i.e., a combined stream including a first encrypted stream, a second encrypted stream, and a clear stream) for a desired program.