Method for partially encrypting program data
OwnerAnthony J. Wasilewski, Howard G. Pinderinventors
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Abstract
A cable television system provides conditional access to services. The cable television system includes a headend from which service “instances,” or programs, are broadcast and a plurality of set top units for receiving the instances and selectively decrypting the instances for display to system subscribers. The service instances are partially-encrypted using public and/or private keys provided by service providers or central authorization agents. Keys used by the set tops for selective decryption may also be public or private in nature, and such keys may be reassigned at different times to provide a cable television system in which piracy concerns are minimized.
Claims12
A method for providing a program in a conditional access system, the method comprising the steps of:
- selecting a digital bit stream from a plurality of digital bit streams;
- encrypting the selected digital bit stream according to a first encryption method to provide a first encrypted stream;
- encrypting the selected digital bit stream according to a second encryption method to provide a second encrypted stream;
- multiplexing the first encrypted stream, the second encrypted stream, and the plurality of digital bit streams to provide a partially-encrypted stream;
- and
- transmitting the partially-encrypted stream.
A method for providing a plurality of programs in a conditional access system, the method comprising the steps of:
- selecting a plurality of elementary bit streams from a transport stream;
- encrypting a portion of the selected elementary bit stream according to a first encryption method to provide a first encrypted stream;
- encrypting the portion of the selected elementary bit stream according to a second encryption method to provide a second encrypted stream;
- multiplexing the first and second encrypted streams and the remaining portion of the selected elementary bit stream with the transport stream;
- and
- transmitting the multiplexed stream.
Dependencies are inferred from the claim text.