Technique for securely communicating programming content

#The invention relates to a communications technique, and more particularly to a technique for securely communicating programming material originating in a cable TV network to a device outside the network.

#A set-top terminal (STT) serves as a gateway between a user's television and a cable TV network delivering programming content. Such programming content may be delivered as a broadcast. It may also be delivered on an on-demand basis, for which services such as video on demand (VOD), subscription VOD, movies on demand, etc., are offered. In addition, a “network personal video recorder (NPVR)” service has been developed, allowing the user to perform trick mode functions (rewind, fast-forward, pause, etc.) on a presentation of programming content through use of a network. In fact, a network architecture and functionalities for implementing the NPVR service are described, e.g., in International Publication Number WO 2003/093944 published on Nov. 13, 2003. The NPVR service also allows a user to “reserve” past and future programs for his/her review, even if such reserved programs were not identified by the user before their broadcast.

#An STT receives, through the cable TV network, programming content which may be encrypted, e.g., in accordance with the data encryption standard (DES) technique, to secure its delivery. DES is a well known symmetrical cipher which utilizes a single key for both encryption and decryption of messages. Because the DES algorithm is publicly known, learning the DES key would allow an encrypted message to be read by anyone. As such, both the message sender and receiver must keep the DES key a secret from others. A DES key typically is a sequence of eight bytes, each containing eight bits. To enhance the DES integrity, the DES algorithm may be applied successive times. With this approach, the DES algorithm enciphers and deciphers data, e.g., three times in sequence, using multiple keys, resulting in a so-called triple DES (3DES) technique.

#Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing showing illustrative embodiments of the invention, in which:

#FIG. 1 illustrates components of a broadband communications system, in accordance with an embodiment of the invention;

#FIG. 2 illustrates a subscriber registry maintained in a headend of the system of FIG. 1;

#The invention is directed to a technique for securely transferring protected programming content from one protective layer to another to prevent unauthorized access and copying of the protected content. One such protective layer is referred to as a “trusted domain.” In a cable TV system, the trusted domain includes not only the system portion where programming content traditionally is secured by, and within total control of, a cable operator, including, e.g., the headend, delivery network, etc., but also user devices at subscribers' premises which are capable of receiving and storing programming content, e.g., a DVR STT, and which implement a conditional access mechanism described below. For the sake of convenience, a DVR STT which implements the conditional access mechanism hereinafter is referred to as a “secure DVR STT (SDVR STT).”

#The cable operator can control certain subscriber access and usage with respect to content held within the trusted domain. For example, a motion picture held within a cable operator's trusted domain (e.g., on a hard drive of an SDVR STT) cannot be distributed over the Internet in viewable form and cannot become a source for duplication of multiple viewable copies. In accordance with the invention, a multi-layered rights arrangement is instituted to facilitate secure transfer of content from one protective layer (e.g., the trusted domain) to another (e.g., outside the trusted domain). In an illustrative embodiment, a first device within the trusted domain is allowed to transmit protected content to a second device outside the trusted domain, provided that the second device recognize and function pursuant to the multi-layered rights arrangement with respect to the protected content. In other words, although the second device outside the trusted domain may receive protected content from the first device in the trusted domain, use and distribution by the second device of the protected content are subject to the rights and restrictions specified by the multi-layered rights arrangement.

#In accordance with the multi-layered rights arrangement, a receiving device may be assigned a security level indicative of the security of the device. In one embodiment, a receiving device may be assigned a security level 1 (low level of trust), 2 (medium level of trust), or 3 (high level of trust). A receiving device's security level determines the set of rights that are accorded to it with respect to the received content.