Methods and apparatus for protecting information content
First Claim
1. A method of processing first, second and third signals for use in a system having first, second, and third signal lines, comprising:
- operating a source device to communicate with a destination device so as to establish a session key;
generating pseudo-random output values based on the session key, using a pseudo-random number generator of the source device,changing, as a function of at least one of said pseudo-random output values, which ones of the first, second, and third signal lines are used to transmit the first, second and third signals, wherein the first, second, and third signals correspond to color signals representing an image and the first, second, and third signal lines couple the source device to the destination device;
as a function of said at least one pseudo-random output value, modifying at least one of the first, second or third signals prior to transmission of said at least one signal over one of said first, second, and third signal lines, the changing including performing a matrix multiplication operation on the first, second, and third signals utilizing matrix coefficients generated from a plurality of the pseudo-random output values; and
utilizing a different session key for each signal line for an image that is transmitted;
wherein session key information is transmitted to the destination device during a video blanking period.
1 Assignment
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Accused Products
Abstract
Methods and apparatus for protecting copyrighted information, e.g., video signals, from unauthorized copying. Analog red (R), green (G) and blue (B) video signals are transmitted from a source device, e.g., a display adapter, to a display device, e.g., a monitor, over corresponding analog signal lines after the identify 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 after the identification of the destination device is confirmed. The source and destination devices each includes a pseudo-random number generator driven by the session key. The lines that carry the R, G and B video signals are changed, e.g., swapped, on a periodic basis as a function of the output of the pseudo-random number generator in the source device. The destination device, which has an input to its pseudo-random number generator synchronized with the random number generator of the source device, decrypts the received video signals in a complimentary fashion to the encryption. Encrypted digital information subject to copying constraints may be supplied to a display adapter via an IEEE 1394 compliant bus.
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Citations
46 Claims
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1. A method of processing first, second and third signals for use in a system having first, second, and third signal lines, comprising:
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operating a source device to communicate with a destination device so as to establish a session key; generating pseudo-random output values based on the session key, using a pseudo-random number generator of the source device, changing, as a function of at least one of said pseudo-random output values, which ones of the first, second, and third signal lines are used to transmit the first, second and third signals, wherein the first, second, and third signals correspond to color signals representing an image and the first, second, and third signal lines couple the source device to the destination device; as a function of said at least one pseudo-random output value, modifying at least one of the first, second or third signals prior to transmission of said at least one signal over one of said first, second, and third signal lines, the changing including performing a matrix multiplication operation on the first, second, and third signals utilizing matrix coefficients generated from a plurality of the pseudo-random output values; and utilizing a different session key for each signal line for an image that is transmitted; wherein session key information is transmitted to the destination device during a video blanking period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of generating encrypted analog first, second and third signals (R′
- , G′
, B′
, respectively) from first, second, and third analog input signals (R, G, B, respectively) the method comprising;seudo-randomly generating at least one of a plurality of matrix coefficients, a1, a2, a3, b1, b2, b3, c1, c2, c3; using an encryption circuit to perform a matrix multiplication operation to generate the encrypted analog first, second, and third signals, according to the following equations;
R′
=a1R+b1G+c1B
G′
=a2R+b2G+c2B
B′
=a3R+b3G+c3Bwherein the matrix coefficients are generated such that each of the R′
, G′ and
B′
signals will be the product of summing two signals in the set of analog signals R, G, B and subtraction one of the signals in the set of analog signals R, G, B. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
- , G′
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22. A communication method comprising the steps of:
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using a pseudo-random number generator to generate output values; and modifying first, second and third signals, by performing a matrix multiplication operation thereon utilizing matrix coefficients which are a function of at least one of the pseudo-random output values, the modified first, second, and third signals being encrypted analog signals so as to define first, second and third encrypted analog signals; and transmitting the first, second and third encrypted analog signals to a destination device; wherein said matrix multiplication involves summing an integer multiple of two of the first, second and third signals and subtracting an integer multiple of another one of said first second and third signals to produce the first encrypted analog signal. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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30. A computer readable medium comprising:
computer executable instructions for controlling a computer device to perform the steps of; operating a pseudo-random number generator to generate a pseudo-random output value; and modifying first, second and third signals, by performing a matrix multiplication operation thereon utilizing matrix coefficients at least one of which is a function of the pseudo-random number output value so as to define first, second and third encrypted analog signals; and transmitting the first, second and third encrypted analog signals to a destination device.
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31. A device, comprising:
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a video signal encryption circuit for encrypting, in response to a pseudo-random number, red green and blue video signals and for producing first, second and third analog encrypted video signals, wherein the video signal encryption circuit comprises a matrix multiplier for performing a matrix multiplication operation on the red, green and blue video signals; a pseudo-random number generator circuit, coupled to the video signal encryption circuit for producing the pseudo-random number value; an input/output interface for outputting the first, second and third encrypted analog video signals. - View Dependent Claims (32, 33, 34, 35)
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36. A method of decrypting encrypted analog signals including the steps of:
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generating a first decrypted analog signal from a first pair of encrypted analog signals by; summing the two encrypted analog signals in the first pair of analog signals to produce a first sum; dividing the first sum by a first value to produce a first decrypted analog signal; and generating a second decrypted analog signal from a second pair of encrypted analog signals by; summing the two encrypted analog signals in the second pair of analog signals to produce a second sum; and dividing the second sum by a second value to produce a second decrypted analog signal; generating a third decrypted analog signal from a third pair of encrypted analog signals by; summing the two encrypted analog signals in the third pair of analog signals to produce a third sum; and dividing the third sum by a third value to produce a third decrypted analog signal comparing values in first and second rows of values to identify a first column in which the first and second rows of values include the same value, wherein the first and second rows of values are first and second rows of values included in a permutation matrix used to encrypt the analog signals included in the first pair of signals; comparing values in second and third rows of values to identify a second column in which the second and third rows of values include the same value, the second column being different than said first column; and controlling which one of a plurality of output lines the first decrypted analog signal is transmitted on as a function of the identified first column and which one of the plurality of output lines the second decrypted analog signal is transmitted on as a function of the identified second column, the first and second decrypted analog signals being transmitted on different output lines. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43)
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44. A method of generating an encrypted analog signal from at least two of a first analog input signal, a second analog input signal, and a third analog input signal, the method comprising:
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pseudo-randomly generating an encryption value, wherein said encryption value is a matrix coefficient and wherein said matrix multiplication operation is performed using analog multipliers; multiplying a first one of said first, second, and third analog input signals with said encryption value to produce a multiplied signal; and combining said multiplied signal with at least a second signal generated from a second one of said first, second and third analog input signals to produce said encrypted analog signal. - View Dependent Claims (45, 46)
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Specification