Cryptography – Key management – Having particular key generator
Patent
1986-04-17
1990-03-13
Buczinski, Stephen C.
Cryptography
Key management
Having particular key generator
380 13, 380 31, 380 38, H04N 7167
Patent
active
049088602
ABSTRACT:
Encoding is realized by means of a first low-pass input filter (21), a first modulator (20), a second low-pass filter (19), a second modulator (18) whose modulating signal has a frequency which is pseudo-random modified in the course of time, which signal is pseudo-random chosen between two signals of different frequencies (45, 46) and an output filter (17). According to the invention a first generator providing two signals is constituted by two phase-locked loop oscillators each having a frequency divider (7, 9) in the loop and both being controlled by the same reference signal generator (3, 4) while the reference signal generator itself is constituted by an oscillator of the same type (3, 4) controlled by the field synchronizing signal of the television transmitter, and this signal as well as the reference signal are applied to a first pseudo-random generator (14) for controlling the instants of change of the modulation signal. Decoding is effected similarly in the reverse order.
REFERENCES:
patent: 3054857 (1962-09-01), Weiss
patent: 4148063 (1979-04-01), Chomet
patent: 4389671 (1983-06-01), Posner et al.
patent: 4398216 (1983-08-01), Field et al.
patent: 4410911 (1983-10-01), Field et al.
Caprarese Vincent
Chretien Thierry
Dauvillier Richard
Buczinski Stephen C.
Gadson Gregory P.
U.S. Philips Corporation
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