Cryptography – Key management – Having particular key generator
Patent
1995-09-27
1998-06-09
Gregory, Bernarr E.
Cryptography
Key management
Having particular key generator
380 9, 380 10, 380 50, H04L 900, H04N 7167
Patent
active
057647739
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to repeating devices, decoder devices and encryption and broadcasting apparatuses and, particularly, to repeating devices, decoder devices and encryption and broadcasting apparatus used in a CATV (Community Antenna TV, Cable TV) or the like which individually receive encrypted broadcasting from an antenna and/or a cable.
BACKGROUND TECHNOLOGY
In recent years, encrypted broadcasting(broadcasting available only for specific viewers) has become more prevalent, and a receiving device for receiving encrypted broadcasting has become more common. Encrypted broadcasting, which uses an encryption and broadcasting apparatus, is arranged such that a broadcasting station encrypts video and audio signals (a process hereinafter referred to as "scrambling") before the signals are transmitted so that persons outside the intended audience who receive the encrypted signals are unable to understand/decipher them. In contrast, the intended audience is provided with decoder devices (hereinafter referred to as "decoders") having a descrambler to decode (a process hereinafter referred to as "descrambling") the scrambled signal, to reproduce the original audio and video signals. Moreover, the arrangement is such that only persons outside the intended audience are prohibited from descrambling the scrambled signal, rendering those persons incapable of receiving the information carried in the scrambled signal.
An example of an encrypting and broadcasting system will be described as an example of a COATEC (COATEC: Conditional Access Technology Research Institute) system, one of the chargeable satellite broadcasting systems which is presently employed or operated in Japan. FIG. 12 shows an arrangement of a transmitter 100 of the broadcasting station on the transmission side in accordance with the COATEC system.
The transmitter 100 uses scramblers 101 and 105 to scramble the video and audio signals. A scramble flag is read by the receiving side to determine whether the scrambled signals have undergone scramble broadcasting on the receiving side. The scramble flag corresponds to the eight bit (hereinafter referred to as "R#8") of a range bit which is multiplexed upon the audio signal and the twelfth bit of the control code (a video scramble flag, hereinafter referred to as "VS") in case the COATEC system.
The scramble flag (hereinafter referred to as "successive sending") is continuously sent (hereinafter referred to as "successive sending") a plurality of times by a successive-sending control part 111 of transmitter 100. The scramble flag is therefore multiplexed upon the scramble audio signal by the multiplexing part 123 before being transmitted. Accordingly, the scramble flag is judged based on parity by a majority judgment part of the decoder on the receiving side to avoid errors. The scramble flag is received by scramblers 101 and 105 of transmitter 100, ON/OFF control of the scrambled video and audio signals is conducted.
A PN signal(otherwise known as a pseudorandom noise) signal or a pseudorandom signal) is sent from the transmitter 100 to the decoder, and is used to scramble and descramble signals. The transmitter 100 and the decoder have respective PN generators for generating the same PN signal. To acquire an identical PN signal in the transmitter 100 and the decoder, the PN initial value (cipher key) KS in the PN generator is set with the same timing used for the video and audio signals.
A scramble timing signal T5 is used to set the PN initial value KS. A majority judgment part of the decoder is able to judge, in majority, the scramble timing TS, and to conduct the protection against the errors. To permit this majority judgment, the transmitter 100 includes successive-sending control part 109 for successively sending the scramble timing TS, and multiplexing part 123 for multiplexing the scramble timing TS upon the scramble audio signal. Transmitter 100 then outputs the multiplexed product. Further, the transmitter 100 inputs the scramble timing TS into PN generators 103 and 107, wh
REFERENCES:
patent: 4995080 (1991-02-01), Bestler et al.
patent: 5018197 (1991-05-01), Jones et al.
patent: 5161192 (1992-11-01), Carter et al.
patent: 5353353 (1994-10-01), Vijeh et al.
patent: 5386470 (1995-01-01), Carter et al.
Electric Communication Technology Deliberative Council Report.
Ministerial ordinance No. 77 and a notification No.803 of Japan Ministry of Posts and Telecommunications relating to televison character multiple broadcasting.
Gregory Bernarr E.
Kabushiki Kaisha Toshiba
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