System for protecting information content

Abstract

System 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.

1 . A system for 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 system comprising: 
 a matrix coefficient generating component configured to pseudo-randomly generate at least one of a plurality of matrix coefficients, a1, a2, a3, b1, b2, b3, c1, c2, c3;    an encryption component configured to use 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′=a 1 R+b 1 G+c 1 B,      G′=a 2 R+b 2 G+c 2 B,      B′=a 3 R+b 3 G+c 3 B;      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 system comprising: 
 a pseudo-random number generator component configured to use a pseudo-random number generator to generate output values;    a matrix multiplication component configured to modify 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    a transmission component configured to transmit 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.    
   
   
       3 . A system for decrypting encrypted analog signals, the system comprising: 
 a first decrypted analog signal generating component configured to generate 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 the first decrypted analog signal;  
   a first comparison component configured to compare 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    a controller component configured to control 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 system of  claim 3 , further comprising: 
 a second decrypted analog signal generating component configured to generate 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 the second decrypted analog signal.  
   
   
   
       5 . The system of  claim 4 , further comprising: 
 a third decrypted analog signal generating component configured to generate 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 the third decrypted analog signal.  
   
   
   
       6 . The system of  claim 5 , wherein the first, second, and third values are the same.  
   
   
       7 . The system of  claim 6 , wherein the first, second, and third values are integer multiples of 2.  
   
   
       8 . The system of  claim 6 , further comprising: 
 a pseudo-random number generator component configured to periodically change the value used for the first, second, and third values as a function of the output of a pseudo-random number generator.    
   
   
       9 . The system of  claim 5 , further comprising: 
 a second comparison component configured to compare 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    wherein the controller component is further configured to control 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 system 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 system of  claim 9 , further comprising: 
 a third comparison component configured to compare 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    wherein the controller component is further configured to control which one of the 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 system of  claim 10 , 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 system 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 are coupled to a display device.