Methods and apparatus for protecting information content

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+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 subtraction one of the signals in the set of analog signals R, G, B.

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 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.

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.

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
• 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.

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, 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.