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US 8,644,362 B1Granted
Hybrid pseudo-random noise and chaotic signal implementation for covert communication
AssigneeThe SI Organization, Inc.
InventorsRobert Lauer, Peter Shaw
Life of this patent
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Abstract
A method and system for covert communication is provided by using a hybrid approach of pseudo-random noise (PN) sequencing with chaotic signals to make a transmitted waveform both hard to detect and hard to intercept by an unintended receiver. The method and system makes a covert communication system with chaotic signals practical for in-field use, including operation in a high noise power environment and allowing for easily changing between different security keys to maintain covertness.
Claims23
A covert communication system comprising:
- a transmitter for sending a covert signal, the transmitter comprising:
- a modulator to modulate a data signal entering the transmitter to create a transmitter modulated signal,
- a first transmitter multiplying device coupled to the modulator to multiply the transmitter modulated signal with a chaotic signal to create a chaotic modulated signal,
- a transmitter chaos generator coupled to the first multiplying device to generate the chaotic signal, wherein the chaotic modulated signal reenters the transmitter chaos generator;
- a transmitter pseudo-random noise sequence generator to generate a transmitter pseudo-random noise sequence, and
- a second transmitter multiplying device coupled to the first multiplying device and to the transmitter pseudo-random noise sequence generator to multiply the chaotic modulated signal with the transmitter pseudo-random noise sequence to create the covert signal;
- and
- a receiver for receiving the covert signal, wherein the receiver comprises:
- a receiver pseudo-random noise sequence generator to generate a receiver pseudo-random noise sequence identical to the transmitter pseudo-random noise sequence,
- a first receiver multiplying device coupled to the receiver pseudo-random noise sequence generator to multiply the covert signal with the pseudo-random noise sequence to create a de-spread signal,
- a receiver chaos generator coupled to the first receiver multiplying device to generate a receiver chaotic signal, wherein the receiver chaos generator is of similar configuration as the transmitter chaos generator and wherein the de-spread signal enters the receiver chaos generator,
- a complex conjugate device coupled to the receiver chaos generator to complex conjugate the receiver chaotic signal to generate a conjugated signal,
- a second receiver multiplying device coupled to the first receiver multiplying device and the complex conjugate device to multiply the conjugated signal to the de-spread signal to create a receiver modulated signal, and
- a demodulator coupled to the second receiver multiplying device to demodulate the receiver modulated signal to generate a received data signal approximating the data signal entering the transmitter.
11 more elements
A method for covertly communicating between a transmitter and a receiver comprising:
- receiving a data signal at the transmitter;
- modulating the data signal at a modulator in the transmitter to create a transmitter modulated signal;
- generating a chaotic signal from a transmitter chaos generator in the transmitter;
- multiplying the modulated signal with the chaotic signal in the transmitter to create a transmitter chaotic carrier signal;
- generating a transmitter pseudo-random noise sequence from a transmitter pseudo-random noise sequence generator in the transmitter;
- multiplying the transmitter chaotic carrier signal to the transmitter pseudo-random noise sequence in the transmitter to create a covert signal;
- transmitting the covert signal over a channel from the transmitter;
- receiving the covert signal transmitted from the transmitter over the channel at the receiver;
- generating a receiver pseudo-random noise sequence from a receiver pseudo-random noise sequence generator identical to the transmitter pseudo-random noise sequence;
- multiplying the receiver pseudo-random noise sequence to the covert signal in the receiver to create a de-spread signal;
- generating a receiver chaotic carrier signal at a receiver chaos generator, wherein the receiver chaos generator is of similar configuration as the transmitter chaos generator;
- complex conjugating the receiver chaotic carrier signal from the receiver chaos generator at a complex conjugate device to generate a conjugated signal in the receiver;
- multiplying the conjugated signal to the de-spread signal to create a receiver modulated waveform;
- and
- demodulating the receiver modulated waveform at a demodulator in the receiver to generate a received data signal approximating the data signal received at the transmitter.
12 more elements
Dependencies are inferred from the claim text.