APPARATUS FOR PARTIAL DUPLICATE AND PARTIAL ENCRYPTION FOR PACKETS, APPRATUS FOR DECRYPTION FOR PACKETS, METHOD OF PARTIAL DUPLICATING AND PARTIAL ENCRYPTING PACKETS, METHOD OF DECRYPTING PACKETS, AND COMPUTER READABLE STORING MEDIUM

摘要

An encryption arrangement for multiple encryption of television programs. A system according to embodiments of the present invention multiple encrypts only a portion of the data required for full presentation of a television program to permit multiple manufacturer's set-top boxes (36 and 136) within a single system. In one embodiment, only critical packets such as those carrying a payload incorporating packetized elementary stream header information is encrypted. By only encrypting a portion of the program, dramatically less bandwidth is consumed that the alternative of multiple encryption of all program data, thus permitting a larger number of multiple conditional access systems in a single cable television system.