Time dispersal encryption of TV signals
AssigneeCommunications Satellite Corporation
InventorsSidney Metzger, Ronald K. Garlow
Life of this patent
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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.
Claims46
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.
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.
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.
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.
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.
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.
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.
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.
Dependencies are inferred from the claim text.