Methods and apparatus for protecting information content

• US 6,983,050 B1
• Filed: 06/30/2000
• Issued: 01/03/2006
• Est. Priority Date: 10/20/1999
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: England, Paul, Yuval, Gideon A., Yacobi, Yacov
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): HOFFMAN, BRANDON S
• Application Number:
  US09/609,019
• Time in Patent Office: 2,013 Days
• Field of Search: 380/210, 380/213, 380/205, 380/212, 375/130
• US Class Current: 380/210
• CPC Class Codes: H04N 21/4122 additional display device, e.g. video projector digital output for controlling a plurality of local displays G06F3/1423
• CPC Class Codes: H04N 21/43632 involving a wired protocol, e.g. IEEE 1394 high-speed IEEE 1394 serial bus H04L12/40052
• CPC Class Codes: H04N 21/4367 Establishing a secure communication between the client and a peripheral device or smart card
• CPC Class Codes: H04N 21/4402 involving reformatting operations of video signals for household redistribution, storage or real-time display details of conversion of video standards at pixel level H04N7/01; video transcoding H04N19/40; adapting incoming signals to the display format of the display terminal G09G5/005; media handling at the source in data packet switching networks H04L65/764
• CPC Class Codes: H04N 21/4405 involving video stream decryption
• CPC Class Codes: H04N 21/4408 involving video stream encryption, e.g. re-encrypting a decrypted video stream for redistribution in a home network
• CPC Class Codes: H04N 7/1696 by changing or reversing the order of active picture signal portions

Abstract

Methods and apparatus for protecting copyrighted information, e.g., video signals, from unauthorized coping. 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 S 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 constraint may be supplied to a display adapter via an IEEE 1399 compliant bus.

Claims

1. 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;

pseudo-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+c3B

wherein 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 subtracting one of the signals in the set of analog signals R, G, B.

2. A communication method comprising the steps of:

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 multiplications 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.

3. A method of decrypting encrypted analog signals including the steps of:

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 further comprising;

comparing values in first and second rows of values to identify a first column of values in which the first and second rows of values include the same value; and

controlling which one of a plurality of output lines the first decrypted analog signal is transmitted on as a function of the identified column values.

4. The method of claim 3, further comprising:

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.

5. The method of claim 4, further comprising:

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.

6. The method of claim 5, wherein the first second and third values are the same.

7. The method of claim 6, wherein the first second and third values are integer multiples of 2.

8. The method of claim 6, further comprising the step of:

periodically changing the value used for the first, second and third values as a function of the output of a pseudo random number generator.

9. The method of claim 5, further comprising:

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;

comparing values in second and third rows of values to identify a second column in which the second and third rows of values includes 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.

10. The method of claim 9, 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.

11. The method of claim 9, further comprising:

comparing, values in a third row of values and

said first row of values to identify a third column in which the third and first rows of values include the same value; and

controlling which one of a plurality of output lines the third decrypted analog signal is transmitted on as a function of the identified third column, the third decrypted analog signal being transmitted on a different output line from said first and second decrypted analog signals.

12. The method of claim 10, 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;

wherein the second and third rows of values are Second and third rows of values included in said permutation matrix; and

wherein the third and first rows of values are third and first rows of Values included in said permutation matrix.

13. The method of claim 9,

wherein the first, second and third decrypted analog signals are red, green and blue analog video signals;

and

wherein the plurality of output lines include red, green and blue output lines which ere coupled to a display device.

14. 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:

pseudo-randomly generating an encryption value;

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;

wherein said encryption value is a matrix coefficient and wherein said matrix multiplication operation is performed using analog multipliers.