Importance

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Abstract

A method for encrypting programming in which a controlled number of unintended recipients of a broadcast are allowed to view a program so that a set of encryption keys can be found which enables a broadcaster to more quickly broadcast the program to its intended paying recipients than conventional encryption methods which only allow programs to be viewed by its intended recipients. To find the set of keys, a broadcaster first determines an acceptable f-ratio of a total number of viewers of the broadcast program to a number of intended viewers in an identified target set who paid to receive the program. The target set of viewers is included in the total number of viewers. The broadcaster then constructs an f-redundant establishment key allocation set from which the establishment keys for encrypting the program are selected. The establishment key allocation set includes keys for the unintended viewers, and can be implemented as a tree having descending levels of sets with higher level sets having larger populations of viewers. An approximation algorithm is then used to select a key cover set of establishment keys from the establishment key allocation set, wherein the keys in the cover set are used to encrypt the program. The key cover set uses fewer establishment keys to encrypt a program than conventional encryption methods, thereby resulting in fewer transmissions being required to broadcast a program to all of its intended paying recipients and thus providing a more efficient and less expensive method of broadcasting encrypted programming.

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First Claim