Secure modulation and demodulation

• US 20080181402A1
• Filed: 01/10/2008
• Published: 07/31/2008
• Est. Priority Date: 04/07/2003
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Optichron, Inc. (Broadcom, Inc.)
• Inventors: Batruni, Roy G.
• Granted Patent: US 8,340,294 B2
• Time in Patent Office: Days
• US Class Current: 380/255
• CPC Class Codes: H04K 1/00 Secret communication
• CPC Class Codes: H04L 27/00 Modulated-carrier systems
• CPC Class Codes: H04L 9/0668 producing a non-linear pseudorandom sequence

Abstract

A system and method are disclosed for securely transmitting and receiving a signal. A nonlinear keying modulator is used in the transmitter to encrypt the signal using a nonlinear keying modulation technique. A nonlinear keying demodulator is used in the receiver to decrypt the signal.

Claims

1. A transmitter for securely transmitting a signal, including:

an input interface for receiving the signal; and

a nonlinear keying modulator configured to encrypt the signal using a nonlinear keying modulation technique; and

wherein the nonlinear keying modulator has an associated nonlinear keying demodulator with a transfer function that is an inverse of the nonlinear transfer function and that can be used to decrypt a nonlinear keying modulation encrypted signal.

2. A transmitter for securely transmitting a signal as recited in claim 1, wherein the nonlinear keying modulator is configured to encrypt the signal to be decrypted by a receiver.

3. A transmitter for securely transmitting a signal as recited in claim 1, wherein the nonlinear keying modulator is configured to encrypt the signal to be decrypted by a receiver by exchanging a key.

4. A transmitter for securely transmitting a signal as recited in claim 1, further including a linear modulator configured to linearly modulate the signal.

5. A transmitter for securely transmitting a signal as recited in claim 1, further including a linear modulator configured to linearly modulate the signal;

wherein the nonlinear keying modulator nonlinearly modulates the output of the linear modulator.

6. A transmitter for securely transmitting a signal as recited in claim 1, further including a linear modulator configured to linearly modulate the signal, wherein the linear modulator linearly modulates the output of the nonlinear keying modulator.

7. A transmitter for securely transmitting a signal as recited in claim 1, wherein the nonlinear keying modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements.

8. A transmitter for securely transmitting a signal as recited in claim 1, wherein the nonlinear keying modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

and the plurality of nonlinear elements include a minimum-maximum processor.

9. A transmitter for securely transmitting a signal as recited in claim 1, wherein the nonlinear keying modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

and the combination network is a minimum-maximum switching matrix.

10. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear keying modulator includes a plurality of linear filters having a number of filter coefficients, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements; and

the nonlinear keying modulator is adjustable by varying the number of filter coefficients.

11. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements;

wherein the plurality of linear filters include a plurality of feedforward filters; and

the nonlinear keying modulator is adjustable by varying the number of feedforward filters.

12. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements;

wherein the plurality of linear filters include a plurality of feedback filters; and

the nonlinear keying modulator is adjustable by varying the number of feedback filters.

13. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements; and

the nonlinear keying modulator is adjustable by varying the topology of the combination network.

14. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear keying modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements; and

the poles of the plurality of linear filters are inside a unit circle.

15. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear keying modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements; and

the zeros of the plurality of linear filters are inside a unit circle.

16. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear keying modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

the nonlinear keying modulator is configured by receiving a key derived from the configurations of a receiver.

17. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear keying modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

the nonlinear keying modulator is configured by receiving a key derived from the configurations of a receiver; and

each of the plurality of linear filters is configured to be the inverse of a corresponding linear filter in the receiver.

18. A transmitter for securely transmitting a signal as recited in claim 1, wherein:

the nonlinear keying modulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

the plurality of nonlinear elements are a plurality of minimum-maximum processors;

the nonlinear keying modulator is configured by receiving a key derived from the configurations of a receiver; and

the function of each of the plurality of minimum-maximum processors is configured to be the inverse of a corresponding minimum-maximum processor in the receiver.

19. A transmitter for securely transmitting a signal as recited in claim 1, wherein the nonlinear keying modulator is a first nonlinear keying modulator;

and the transmitter further includes a second nonlinear keying modulator coupled to the first nonlinear keying modulator.

20. A transmitter for securely transmitting a signal as recited in claim 1, wherein the nonlinear keying modulator is a first nonlinear keying modulator;

and the transmitter further includes a second nonlinear keying modulator coupled to the first nonlinear keying modulator in a cascaded configuration.

21. A receiver for decrypting a securely transmitted signal, including:

an input interface for receiving the signal; and

a nonlinear keying demodulator configured to decrypt the signal using a nonlinear keying demodulation technique; and

wherein the nonlinear keying demodulator has an associated nonlinear keying modulator with a transfer function that is an inverse of the nonlinear transfer function and that can be used to encrypt a signal.

22. A receiver for decrypting a securely transmitted signal as recited in claim 21, further including a linear demodulator configured to linearly demodulate the signal.

23. A receiver for decrypting a securely transmitted signal as recited in claim 21, further including a linear demodulator configured to linearly demodulate the signal;

wherein the nonlinear keying demodulator nonlinearly demodulates the output of the linear demodulator.

24. A receiver for decrypting a securely transmitted signal as recited in claim 21, further including a linear demodulator configured to linearly demodulate the signal, wherein the linear demodulator linearly demodulates the output of the nonlinear keying demodulator.

25. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein the nonlinear keying demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements.

26. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein the nonlinear keying demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

and the plurality of nonlinear elements include a minimum-maximum processor.

27. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein the nonlinear keying demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

and the combination network is a minimum-maximum switching matrix.

28. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein:

the nonlinear keying demodulator includes a plurality of linear filters having a number of filter coefficients, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements; and

the nonlinear keying demodulator is adjustable by varying the number of filter coefficients.

29. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein:

the nonlinear demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements;

wherein the plurality of linear filters include a plurality of feedforward filters; and

the nonlinear keying demodulator is adjustable by varying the number of feedforward filters.

30. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein:

the nonlinear demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements;

wherein the plurality of linear filters include a plurality of feedback filters; and

the nonlinear keying demodulator is adjustable by varying the number of feedback filters.

31. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein:

the nonlinear demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the linear filters and nonlinear elements; and

the nonlinear keying demodulator is adjustable by varying the topology of the combination network.

32. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein:

the nonlinear keying demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements; and

the poles of the plurality of linear filters are inside a unit circle.

33. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein:

the nonlinear keying demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements; and

the zeros of the plurality of linear filters are inside a unit circle.

34. A receiver for decrypting a securely transmitted signal as recited in claim 22, wherein:

the nonlinear keying demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

the nonlinear keying demodulator is configured by receiving a key derived from the configurations of a transmitter.

35. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein:

the nonlinear keying demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

the nonlinear keying demodulator is configured by receiving a key derived from the configurations of a transmitter; and

each of the plurality of linear filters is configured to be the inverse of a corresponding linear filter in the transmitter.

36. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein:

the nonlinear keying demodulator includes a plurality of linear filters, a plurality of nonlinear elements and a combination network connecting the plurality of linear filters and the plurality of nonlinear elements;

the plurality of nonlinear elements are a plurality of minimum-maximum processors;

the nonlinear keying demodulator is configured by receiving a key derived from the configurations of a transmitter; and

the function of each of the plurality of minimum-maximum processors is configured to be the inverse of a corresponding minimum-maximum processor in the transmitter.

37. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein the nonlinear keying demodulator is a first nonlinear keying demodulator;

and the receiver further includes a second nonlinear keying demodulator coupled to the first nonlinear keying demodulator.

38. A receiver for decrypting a securely transmitted signal as recited in claim 21, wherein the nonlinear keying demodulator is a first nonlinear keying demodulator;

and the receiver further includes a second nonlinear keying demodulator coupled to the first nonlinear keying demodulator in a cascaded configuration.