Abstract: A method and apparatus are disclosed for designing multi-ring networks based on generalized quadrangles of combinatorial design theory, together with a scaling algorithm for realizing networks of arbitrary size. Multi-ring networks based on generalized quadrangles ensures that the path between any two nodes is either confined to a single ring, or traverses exactly two rings (passing through a single bridge node), referred to herein as the “one-bridge property.” The one-bridge property allows the construction of networks with small rings and low degree, while also permitting efficient congestion-free flow control protocols. Routing, access and flow control protocols are provided for the multi-ring network that capitalize on the combinatorial properties of the disclosed multi-ring networks. A “self-routing” routing protocol is disclosed wherein a source node does not need to know how to route a packet to a destination node that is not a neighbor.

Abstract: A system for restricting access to transmitted programming content is disclosed, which transmits a program identifier with the encrypted programming content. A set-top terminal or similar mechanism restricts access to the transmitted multimedia information using stored decryption keys. The set-top terminal preferably receives entitlement information periodically from the head-end, corresponding to one or more packages of programs that the customer is entitled to for a given period. Each program is preferably encrypted by the head-end server prior to transmission, using a program key, Kp, which may be unique to the program. The set-top terminal uses the received program identifier, p, together with the stored entitlement information, to derive the decryption key necessary to decrypt the program. Each of the k-bit program keys, Kp, used to encrypt transmitted programs is a linear combination of a defined set of k-bit master keys, m1 . . . m1.

Abstract: A system for detecting the movement of a device that receives a signal broadcast from a relative fixed position, such as a set-top terminal in a Direct Broadcast Satellite (DBS) system, is disclosed, using the phase shift of the broadcast signal, as received by the device. A set-top terminal or similar mechanism restricts access to the transmitted multimedia information using stored decryption keys. If a set-top terminal is moved, the distance between the set-top terminal and the satellite will change, thereby causing a measurable phase shift in the signal received by the set-top terminal. The set-top terminal periodically or intermittently records a sequence of bits received from the satellite and provides the recorded bits to the service provider server for analysis. If the set-top terminal has been moved, the recorded bits will shift.

Abstract: A system for restricting access to transmitted programming content is disclosed, which transmits the encryption key used to encrypt the program to the customer with the encrypted programming content. A set-top terminal or similar mechanism restricts access to the transmitted multimedia information using stored decryption keys. The set-top terminal preferably receives one or more package keys, S.sub.J, periodically from the service provider, each corresponding to a package of programs that the customer is entitled to for a given period. Each program is preferably encrypted by the head-end server prior to transmission using a program key, K.sub.P, which may be unique to the program. Header information is transmitted with the encrypted program to the customers, containing a package pair for each package to which the program belongs. A package pair preferably includes an identifier of the package, as well as the program key, K.sub.P, encrypted by the corresponding package key, S.sub.J.