US4901349A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Time dispersal encryption of TV signals
Assignee: Comsat Corp
•
Filing: 1987-12-31
•
Granted: 1990-02-13
•
Expires: 2007-12-31
Abstract
Abstract In encrypting a video signal for communications security, the horizontal synchronization pulses are removed, the active signal portions of each line in a field are delayed according to psuedorandom sequence of delays, and the reference color burst is moved to a position in the horizontal blanking interval which is constant for all lines irrespective of their individual delays. The process is reversed for decryption.
Inventors
- 👤 Sidney Metzger
- 👤 Ronald K. Garlow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 17:05
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/16; H04N7/167; H04N7/1675; H04N7/169; H04N7/171; H04N7/1713
Claims Analysis
Total Claims: 54
Claim 1
Independent Claim
103 words
A method of encrypting video signals of the type comprising a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines of an original video signal being separated from one another by horizontal blanking periods including a horizontal synchronization pulse, said method comprising: removing said horizontal synchronization pulses from each horizontal blanking period; delaying the active signal portion of each line with respect to said original video signal by a respective delay period less than the duration of a horizontal blanking period; and periodically changing said delay period.
Claim 2
Independent Claim
103 words
A method of encrypting video signals of the type comprising a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines of an original video signal being separated from one another by horizontal blanking periods including a horizontal synchronization pulse, said method comprising: removing said horizontal synchronization pulses from each horizontal blanking period; delaying the active signal portion of each line with respect to said original video signal by a respective delay period less than the duration of a horizontal blanking period; and periodically changing said delay period.
Claim 3
Dependent Claim
24 words
A method as defined in claim 1, wherein said step of periodically changing said delay period comprises changing said delay period between successive lines.
Claim 4
Dependent Claim
40 words
A method as defined in claim 2, wherein said video signal includes successive fields of plural lines, and wherein the active signal portions of successive lines in a field are delayed in accordance with a pseudorandom sequence of delay periods.
Claim 5
Dependent Claim
80 words
A method as defined in claim 1, wherein said video signal includes successive fields of plural lines, and wherein each field includes a first portion representing an image to be displayed said method further comprising the steps of: generating a sequence code identifying the sequence of delays to be imparted to the active signal portions of successive lines in a particular field; and transmitting said sequence code with said video signal prior to the first portion of said particular field.
Claim 6
Dependent Claim
79 words
A method as defined in claim 2, wherein said video signal includes successive fields of plural lines, and wherein each field includes a first portion representing an image to be displayed, said method further comprising the steps of: generating a sequence code identifying the sequence of delays to be imparted to active signal portions of successive lines in a particular field; and transmitting said sequence code with said video signal prior to the first portion of said particular field.
Claim 7
Dependent Claim
68 words
A method as defined in claim 1, wherein said video signal further includes a color reference burst following said horizontal synchronizing signal in said horizontal blanking period, said method further comprising the step of shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period.
Claim 8
Dependent Claim
25 words
A method as defined in claim 2, wherein the maximum delay imparted to the active signal portion of any one line is approximately seven microseconds.
Claim 9
Dependent Claim
60 words
A method as defined in claim 2, wherein said video signal further includes a color reference burst following said horizontal synchronizing signal in said horizontal blanking period, and wherein the maximum delay imparted to the active signal portion of any one line is equal to the duration of a horizontal blanking period less the duration of said color reference burst.
Claim 10
Dependent Claim
72 words
A method as defined in claim 8 further comprising the step of shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period, said shifted color reference burst beginning said maximum delay period after the end of the active signal portion of an undelayed line of said video signal.
Claim 11
Independent Claim
169 words
A method of securely transmitting video signals from a transmitting station and receiving said video signals at a receiving station, said video signals being of the type including a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines of an original video signal being separated from one another by horizontal blanking periods including a horizontal synchronizing pulse, said method comprising: removing said horizontal synchronization pulse from each horizontal blanking period; delaying the active signal portions with respect to said original video signal by different delay periods less than the duration of a horizontal blanking period to obtain an encrypted video signal; transmitting said encrypted video signal to said receiving station; and at said receiving station, delaying the active signal portions of the encrypted video signal by a delay period which is the complement of the delay imparted to each active signal portion at said transmitting station to thereby obtain a decrypted video signal.
Claim 12
Independent Claim
169 words
A method of securely transmitting video signals from a transmitting station and receiving said video signals at a receiving station, said video signals being of the type including a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines of an original video signal being separated from one another by horizontal blanking periods including a horizontal synchronizing pulse, said method comprising: removing said horizontal synchronization pulse from each horizontal blanking period; delaying the active signal portions with respect to said original video signal by different delay periods less than the duration of a horizontal blanking period to obtain an encrypted video signal; transmitting said encrypted video signal to said receiving station; and at said receiving station, delaying the active signal portions of the encrypted video signal by a delay period which is the complement of the delay imparted to each active signal portion at said transmitting station to thereby obtain a decrypted video signal.
Claim 13
Dependent Claim
22 words
A method as defined in claim 10, wherein said first delaying step comprises changing said delay period between successive active signal portions.
Claim 14
Dependent Claim
44 words
A method as defined in claim 10, wherein said video signal includes successive fields of plural lines, and wherein said first delaying step comprises delaying the active signal portions of successive lines in a field in accordance with a pseudorandom sequence of delay periods.
Claim 15
Dependent Claim
109 words
A method as defined in claim 10, wherein said video signal includes successive fields of plural lines, and wherein each field includes a first portion representing an image to be displayed, said method further comprising the steps of: generating a sequence code identifying the sequence of delays to be imparted at said transmitting station to the active signal portions of successive lines in a particular field; transmitting said sequence code with said encrypted video signal prior to the first portion of said particular field; detecting said sequence code at said receiving station: and delaying the active signal portions of said encrypted video signal in accordance with said sequence code.
Claim 16
Dependent Claim
80 words
A method as defined in claim 11, wherein said video signal includes successive fields of plural lines, and wherein each field includes a first portion representing an image to be displayed, said method further comprising the steps of: generating a sequence code identifying the sequence of delays to be imparted at said transmitting station to successive lines in a particular field; and transmitting said sequence code with said encrypted video signal prior to the first portion of said particular field.
Claim 17
Dependent Claim
72 words
A method as defined in claim 10, wherein said video signal further includes a color reference burst following said horizontal synchronizing signal in said horizontal blanking period, said method further comprising the step of shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period at said transmitting station.
Claim 18
Dependent Claim
25 words
A method as defined in claim 11, wherein the maximum delay imparted to the active signal portion of any one line is approximately seven microseconds.
Claim 19
Dependent Claim
60 words
A method as defined in claim 11, wherein said video signal further includes a color reference burst following said horizontal synchronizing signal in said horizontal blanking period, and wherein the maximum delay imparted to the active signal portion of any one line is equal to the duration of a horizontal blanking period less the duration of said color reference burst.
Claim 20
Dependent Claim
73 words
A method as defined in claim 17, further comprising the step of shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of the lines before and after each said horizontal blanking period said shifted color reference burst beginning said maximum delay period after the end of the active signal portion of an undelayed line of said video signal.
Claim 21
Independent Claim
99 words
An apparatus for encrypting video signals of the type comprising a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines of an original video signal being separated from one another by horizontal blanking periods including a horizontal synchronization pulse, said apparatus comprising: means for removing said horizontal synchronization pulses from each horizontal blanking period; and delay means for delaying the active signal portions with respect to said original video signal by different delay periods less than the duration of a horizontal blanking period.
Claim 22
Independent Claim
99 words
An apparatus for encrypting video signals of the type comprising a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines of an original video signal being separated from one another by horizontal blanking periods including a horizontal synchronization pulse, said apparatus comprising: means for removing said horizontal synchronization pulses from each horizontal blanking period; and delay means for delaying the active signal portions with respect to said original video signal by different delay periods less than the duration of a horizontal blanking period.
Claim 23
Dependent Claim
22 words
An apparatus as defined in claim 19, wherein said means for delaying comprises means for changing said delay period between successive lines.
Claim 24
Dependent Claim
42 words
An apparatus as defined in claim 20, wherein said video signal includes successive fields of plural lines, and wherein said delaying means delays the active signal portions of successive lines in a field in accordance with a pseudorandom sequence of delay periods.
Claim 25
Dependent Claim
81 words
An apparatus as defined in claim 19, wherein said video signal includes successive fields of plural lines, and wherein each field includes a first portion representing an image to be displayed, said apparatus further comprising: means for generating a sequence code identifying the sequence of delays to be imparted to the active signal portions of successive lines in a particular field; and means for transmitting said sequence code with said video signal prior to the first portion of said particular field.
Claim 26
Dependent Claim
80 words
An apparatus as defined in claim 20, wherein said video signal includes successive fields of plural lines, and wherein each field includes a first portion representing an image to be displayed, said apparatus further comprising: means for generating a sequence code identifying the sequence of delays to be imparted to active signal portions of successive lines in a particular field; and means for transmitting said sequence code with said video signal prior to the first portion of said particular field.
Claim 27
Dependent Claim
67 words
An apparatus as defined in claim 19, wherein said video signal further includes a color reference burst following said horizontal synchronizing signal in said horizontal blanking period, said apparatus further comprising means for shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period.
Claim 28
Dependent Claim
25 words
An apparatus as defined in claim 20, wherein the maximum delay imparted to the active signal portion of any one line is approximately seven microseconds.
Claim 29
Dependent Claim
60 words
An apparatus as defined in claim 20, wherein said video signal further includes a color reference burst following said horizontal synchronizing signal in said horizontal blanking period and wherein the maximum delay imparted to the active signal portion of any one line is equal to the duration of a horizontal blanking period less the duration of said color reference burst.
Claim 30
Dependent Claim
71 words
An apparatus as defined in claim 26, further comprising means for shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period, said shifted color reference burst beginning said maximum delay period after the end of the active signal portion of an undelayed line of said video signal.
Claim 31
Dependent Claim
34 words
An apparatus as defined in claim 22, wherein said video signal is accompanied by an audio signal portion, said apparatus further comprising means for encrypting said audio information in accordance with said sequence code.
Claim 32
Dependent Claim
64 words
An apparatus as defined in claim 19, wherein said delay means comprises: means for receiving said video signal and providing a plurality of delayed versions thereof; selection means responsive to a control signal for selecting one of said delayed versions; and means for generating said control signal in accordance with a desired sequence of delay periods for the active signal portions of successive lines.
Claim 33
Dependent Claim
76 words
An apparatus as defined in claim 19, wherein said delay means comprises: first storage means for receiving and storing at least one line of said video signal at a succession of memory locations; means for providing a succession of readout signals to said storage means for reading said video signal out of said storage means; and means for interrupting said succession of readout signals for the predetermined delay period associated with said at least one line.
Claim 34
Dependent Claim
29 words
An apparatus as defined in claim 30, wherein said delay means comprises first and second storage means for alternately storing and reading out the video signal for successive lines.
Claim 35
Dependent Claim
25 words
An apparatus as defined in claim 31, wherein said first and second storage means comprise CCD delay lines and said readout signals comprise clock signals.
Claim 36
Dependent Claim
25 words
An apparatus as defined in claim 31, wherein said first and second storage means comprise random access memories and said readout signals comprise address signals.
Claim 37
Independent Claim
178 words
An apparatus of securely transmitting video signals from a transmitting station and receiving said video signals at a receiving station, said video signals being of the type including a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines of an original video signal being separated from one another by horizontal blanking periods including a horizontal synchronization pulse, said apparatus comprising: means for removing said horizontal synchronization pulse from each horizontal blanking period; first delay means for delaying the active signal portions with respect to said original video signal by different delay periods less than the duration of a horizontal blanking period to obtain an encrypted video signal; means for transmitting said encrypted video signal to said receiving station; and second delay means for delaying the active signal portions of the encrypted video signal by a delay period which is the complement of the delay imparted to each active signal portion by said first delay means, to thereby obtain a decrypted video signal.
Claim 38
Independent Claim
178 words
An apparatus of securely transmitting video signals from a transmitting station and receiving said video signals at a receiving station, said video signals being of the type including a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines of an original video signal being separated from one another by horizontal blanking periods including a horizontal synchronization pulse, said apparatus comprising: means for removing said horizontal synchronization pulse from each horizontal blanking period; first delay means for delaying the active signal portions with respect to said original video signal by different delay periods less than the duration of a horizontal blanking period to obtain an encrypted video signal; means for transmitting said encrypted video signal to said receiving station; and second delay means for delaying the active signal portions of the encrypted video signal by a delay period which is the complement of the delay imparted to each active signal portion by said first delay means, to thereby obtain a decrypted video signal.
Claim 39
Dependent Claim
24 words
An apparatus as defined in claim 34, wherein said first delay means comprises means for changing said delay period between successive active signal portions.
Claim 40
Dependent Claim
46 words
An apparatus as defined in claim 34, wherein said video signal includes successive fields of plural lines, and wherein said first delay means comprises means for delaying the active signal portions of successive lines in a field in accordance with a pseudorandom sequence of delay periods.
Claim 41
Dependent Claim
115 words
An apparatus as defined in claim 34, wherein said video signal includes successive fields of plural lines, and wherein each field includes a first portion representing an image to be displayed, said apparatus further comprising: means for generating a sequence code identifying the sequence of delays to be imparted to the active signal portions of successive lines in a particular field; means for transmitting said sequence code with said encrypted video signal prior to the first portion of said particular field; means for detecting said sequence code at said receiving station; and said second delay means comprising means for delaying the active signal portions of said encrypted video signal in accordance with said sequence code.
Claim 42
Dependent Claim
77 words
An apparatus as defined in claim 35, wherein said video signal includes successive fields of plural lines, and wherein each field includes a first portion representing an image to be displayed, said apparatus further comprising: means for generating a sequence code identifying the sequence of delays to be imparted to successive lines in a particular field; and means for transmitting said sequence code with said encrypted video signal prior to the first portion of said particular field.
Claim 43
Dependent Claim
72 words
An apparatus as defined in claim 34, wherein said video signal further includes a color reference burst following said horizontal synchronizing signal in said horizontal blanking period, said apparatus further comprising means for shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted by said first delay means to the active signal portions of lines before and after each said horizontal blanking period.
Claim 44
Dependent Claim
25 words
An apparatus as defined in claim 35, wherein the maximum delay imparted to the active signal portion of any one line is approximately seven microseconds.
Claim 45
Dependent Claim
60 words
An apparatus as defined in claim 35, wherein said video signal further includes a color reference burst following said horizontal synchronizing signal in said horizontal blanking period, and wherein the maximum delay imparted to the active signal portion of any one line is equal to the duration of a horizontal blanking period less the duration of said color reference burst.
Claim 46
Dependent Claim
77 words
An apparatus as defined in claim 41, further comprising means for shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted by said first delay means to the active signal portions of the lines before and after each said horizontal blanking period, said shifted color reference burst beginning said maximum delay period after the end of the active signal portion of an undelayed line of said video signal.
Claim 47
Independent Claim
121 words
A method of encrypting video signals of the type comprising a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines being separated from one another by horizontal blanking periods including a horizontal synchronization pulse and a color reference burst following said horizontal synchronizing signal, said method comprising: removing said horizontal synchronization pulses from each horizontal blanking period; delaying the active signal portion of each line by a respective delay period; and shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period.
Claim 48
Independent Claim
121 words
A method of encrypting video signals of the type comprising a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines being separated from one another by horizontal blanking periods including a horizontal synchronization pulse and a color reference burst following said horizontal synchronizing signal, said method comprising: removing said horizontal synchronization pulses from each horizontal blanking period; delaying the active signal portion of each line by a respective delay period; and shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period.
Claim 49
Independent Claim
196 words
A method of securely transmitting video signals from a transmitting station and receiving said video signals at a receiving station, said video signals being of the type including a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines being separated from one another by horizontal blanking periods including a horizontal synchronization pulse and a color reference burst following said horizontal synchronizing signal, said method comprising: removing said horizontal synchronization pulse from each horizontal blanking period; delaying the active signal portions by different delay periods to obtain an encrypted video signal; transmitting said encrypted video signal to said receiving station; at said receiving station, delaying the active signal portions of the encrypted video signal by a delay period which is the complement of the delay imparted to each active signal portion at said transmitting station to thereby obtain a decrypted video signal; and shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period at said transmitting station.
Claim 50
Independent Claim
196 words
A method of securely transmitting video signals from a transmitting station and receiving said video signals at a receiving station, said video signals being of the type including a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines being separated from one another by horizontal blanking periods including a horizontal synchronization pulse and a color reference burst following said horizontal synchronizing signal, said method comprising: removing said horizontal synchronization pulse from each horizontal blanking period; delaying the active signal portions by different delay periods to obtain an encrypted video signal; transmitting said encrypted video signal to said receiving station; at said receiving station, delaying the active signal portions of the encrypted video signal by a delay period which is the complement of the delay imparted to each active signal portion at said transmitting station to thereby obtain a decrypted video signal; and shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period at said transmitting station.
Claim 51
Independent Claim
124 words
An apparatus for encrypting video signals of the type comprising a plurality of lines each having an active signal portion representing a line of image to be displayed, within the active signal portions of successive lines being separated from one another by horizontal blanking periods including a horizontal synchronization pulse and a color reference burst following said horizontal synchronizing signal, said apparatus comprising: means for removing said horizontal synchronization pulses from each horizontal blanking period; delay means for delaying the active signal portions by different delay periods; and means for shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period.
Claim 52
Independent Claim
124 words
An apparatus for encrypting video signals of the type comprising a plurality of lines each having an active signal portion representing a line of image to be displayed, within the active signal portions of successive lines being separated from one another by horizontal blanking periods including a horizontal synchronization pulse and a color reference burst following said horizontal synchronizing signal, said apparatus comprising: means for removing said horizontal synchronization pulses from each horizontal blanking period; delay means for delaying the active signal portions by different delay periods; and means for shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted to the active signal portions of lines before and after each said horizontal blanking period.
Claim 53
Independent Claim
208 words
An apparatus of securely transmitting video signals from a transmitting station and receiving said video signals at a receiving station, said video signals being of the type including a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines being separated from one another by horizontal blanking periods including a horizontal synchronization pulse and a color reference burst following said horizontal synchronizing signal, said apparatus comprising: means for removing said horizontal synchronization pulse from each horizontal blanking period; first delay means for delaying the active signal portions by different delay periods to obtain an encrypted video signal; means for transmitting said encrypted video signal to said receiving station; second delay means and delaying the active signal portions of the encrypted video signal by a delay period which is the complement of the delay imparted to each active signal; portion by said first delay means, to thereby obtain a decrypted video signal; and means for shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted by said first delay means to the active signal portions of lines before and after each said horizontal blanking period.
Claim 54
Independent Claim
208 words
An apparatus of securely transmitting video signals from a transmitting station and receiving said video signals at a receiving station, said video signals being of the type including a plurality of lines each having an active signal portion representing a line of image to be displayed, with the active signal portions of successive lines being separated from one another by horizontal blanking periods including a horizontal synchronization pulse and a color reference burst following said horizontal synchronizing signal, said apparatus comprising: means for removing said horizontal synchronization pulse from each horizontal blanking period; first delay means for delaying the active signal portions by different delay periods to obtain an encrypted video signal; means for transmitting said encrypted video signal to said receiving station; second delay means and delaying the active signal portions of the encrypted video signal by a delay period which is the complement of the delay imparted to each active signal; portion by said first delay means, to thereby obtain a decrypted video signal; and means for shifting said color reference burst to a predetermined position within each horizontal blanking period regardless of the delays imparted by said first delay means to the active signal portions of lines before and after each said horizontal blanking period.
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