Methods and apparatus for protecting signals transmitted between a source and destination device over multiple signal lines
First Claim
1. A method of processing first, second, and third video signals for use in a system having first, second, third and fourth signal lines, wherein the first, second, and third signal lines couple a source device to a destination device, a pseudo-random number generator being contained within the source device, the method comprising:
- operating the source device to communicate with the destination device so as to establish a session key and synchronization information via one or all of the first, second, third and fourth signal lines during a vertical blanking period;
operating the pseudo-random number generator to generate said pseudo-random output values as a function of the established session key;
generating a fourth signal;
generating, using said pseudo-random number generator, pseudo-random output values; and
for each of the first, second, third and fourth signal lines, selecting, for transmission thereon, one of the first, second, third, and fourth signals, the selection being performed in a mutually exclusive manner and as a function of at least one of said pseudo-random output values, the selection also being performed by a matrix multiplication operation performed on the first, second, third and fourth signals utilizing matrix coefficients generated from a plurality of the pseudo-random output values,wherein the first, second and third signals are red, green and blue video signals, respectively, the method further comprising the steps of encrypting horizontal synchronization information into at least one of said red, green and blue video signals prior to changing which ones of the first, second, third and fourth signal lines are used to transmit said first, second and third signals.
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Accused Products
Abstract
Methods and apparatus for protecting copyrighted information, e.g., video signals, from unauthorized use are described. Encrypted video signals are transmitted from a source device, e.g., display adapter, to a display device, e.g., monitor, over analog signal lines after the identity of the destination device is confirmed by receipt of a certificate assigned to the destination device. A session key, used for encrypting the analog signals, is generated and exchanged between the source and destination devices. The source and destination devices each include a pseudo-random number generator driven by the session key. As part of the encryption process a false video signal is generated. The false video signal and R, G, B video signals are transmitted to the display device over four lines. The lines used to transmit the R, G, B and false video signals are periodically swapped as a function of the output of the pseudo random number generator to encrypt, e.g., scramble, the video signals. To avoid having to provide an additional line between the display adapter and the display device beyond those used in conventional displays, horizontal synchronization information is combined with, e.g., modulated on, one or more of the other signals transmitted to the display. The horizontal sync line is then used to convey one of the four video signals. The display device extracts the horizontal timing information from the received video signals and decrypts the signals using the output of its pseudo random number generator to reverse the scrambling process used to encrypt the transmitted video signals.
23 Citations
12 Claims
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1. A method of processing first, second, and third video signals for use in a system having first, second, third and fourth signal lines, wherein the first, second, and third signal lines couple a source device to a destination device, a pseudo-random number generator being contained within the source device, the method comprising:
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operating the source device to communicate with the destination device so as to establish a session key and synchronization information via one or all of the first, second, third and fourth signal lines during a vertical blanking period; operating the pseudo-random number generator to generate said pseudo-random output values as a function of the established session key; generating a fourth signal; generating, using said pseudo-random number generator, pseudo-random output values; and for each of the first, second, third and fourth signal lines, selecting, for transmission thereon, one of the first, second, third, and fourth signals, the selection being performed in a mutually exclusive manner and as a function of at least one of said pseudo-random output values, the selection also being performed by a matrix multiplication operation performed on the first, second, third and fourth signals utilizing matrix coefficients generated from a plurality of the pseudo-random output values, wherein the first, second and third signals are red, green and blue video signals, respectively, the method further comprising the steps of encrypting horizontal synchronization information into at least one of said red, green and blue video signals prior to changing which ones of the first, second, third and fourth signal lines are used to transmit said first, second and third signals. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of processing first, second, and third video signals which are coupling a source device to a destination device, the method comprising:
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generating a fourth video signal; operating the source device to communicate with the destination device so as to establish a session key and synchronization information via one or all of the first, second, third and fourth video signals during a vertical blanking period; transmitting the first, second, third, and fourth video signals over first, second, third and fourth lines, the transmitting including periodically swapping the lines used to transmit the first, second, third and fourth video signals; and modifying at least one of said first, second and third signals prior to transmitting them, the modifying including modulating horizontal synchronization information on each of said first, second, and third video signals, wherein periodically swapping the lines used to transmit the first, second, third and fourth video signals includes the act of performing a matrix multiplication operation on the first, second, third and fourth video signals to determine the line on which each of the video signals are transmitted. - View Dependent Claims (8, 9)
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10. A video adapter comprising:
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a video signal generation means for generating a fourth video signal; a session key establishing means for establishing a session key and communicating synchronization information via one or all of a first, second, third and fourth signal lines during a vertical blanking period; a pseudo-random number generation means for generating pseudo-random output values as a function of the established session key; and selection means for selecting one of the first, second, third, and fourth video signals for transmission over each of the first, second, third and fourth signal lines, wherein the selection means includes use of a matrix multiplier and further comprising means for modulating horizontal synchronization information on one of the first, second, third, and fourth video signals. - View Dependent Claims (11, 12)
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Specification