Cryptography – Particular algorithmic function encoding – Nbs/des algorithm
Patent
1988-09-30
1989-12-26
Tarcza, Thomas H.
Cryptography
Particular algorithmic function encoding
Nbs/des algorithm
358 86, 358145, 358147, 380 21, 455 4, 455 6, H04N 7167, H04N 710, H04N 704
Patent
active
048903213
ABSTRACT:
A subscription television system in which individual decoders are enabled to receive individually addressed messages is disclosed. The composite signal, including video and teletext, also comprises addressed packets which are detected by decoders and which indicate that a message addressed to a particular subscriber is forthcoming, and system control data. In a preferred embodiment, both addressed packets and teletext are encrypted. The addressed packet is decrypted using a decoder-specific code and a transmitted code, while the teletext message is decrypted using a decryption key contained in the system control data. The teletext message cannot be received until the addressed packet has been decrypted. Therefore, redundant levels of security are provided to the system. Messages for display to the user can be selected in response to user initiated commands, in response to decoder initiation, or in response to the transmitter.
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Bates Cameron
Lim Samson
Lucas Keith
Rassel William van
Seth-Smith Nigel
Scientific - Atlanta, Inc.
Tarcza Thomas H.
Wallace Linda J.
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