Cryptography – Key management – Having particular key generator
Patent
1994-12-12
1996-10-01
Buczinski, Stephen C.
Cryptography
Key management
Having particular key generator
348574, 380 42, H04N 7167, H04L 900, H03M 112
Patent
active
055617140
ABSTRACT:
An improved scrambler for serial digital video that is compatible with SMPTE Standard 259M inserts a detector/dithering circuit between the input serial digital signal and a scrambler. The scrambler's statistics are observed by a pair of up/down counters. One counter monitors the scrambled data prior to NRZI encoding to determine transition density, and the other monitors the NRZI encoder output to determine the relative density of "ones" and "zeros" in the scrambled output signal. A pseudorandom generator generates a dither signal which is combined with the least significant bit of selected video words of the input serial digital signal when enabled by the terminal count output from either counter. A complementary descrambler has a similar detector/dithering circuit at its output to restore the original least significant bit of the selected video words. The improved scrambler/descrambler may be implemented in either the serial or the parallel domain. Thus pathological signals are avoided that could create problems within the serial digital video bit stream.
REFERENCES:
patent: 4742543 (1988-05-01), Frederiksen
"Pathological Check Codes for Serial Digital Interface Systems" by Takeo Eguchi, SMPTE Journal, Aug. 1992.
Buczinski Stephen C.
Gray Francis I.
Tektronix Inc.
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