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Method for generating a digital key for secure wireless communication

  • US 10,462,655 B2
  • Filed: 08/31/2016
  • Issued: 10/29/2019
  • Est. Priority Date: 09/01/2015
  • Status: Active Grant
First Claim
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1. A method for generating a first digital key in a first communication device and a second digital key in a second communication device, the method comprising:

  • transmitting a first electromagnetic signal from the first communication device to the second communication device via a reciprocal transmission channel, wherein the first electromagnetic signal is changed by properties of the reciprocal transmission channel;

    estimating the reciprocal transmission channel between the first communication device and the second communication device from the first electromagnetic signal received by the second communication device;

    determining properties of the estimated reciprocal transmission channel;

    generating the second digital key from the properties of the estimated reciprocal transmission channel;

    transmitting a second electromagnetic signal from the second communication device to the first communication device via the reciprocal transmission channel, wherein the second electromagnetic signal is changed by properties of the reciprocal transmission channel;

    estimating the reciprocal transmission channel between the first communication device and the second communication device from the second electromagnetic signal received by the first communication device;

    determining properties of the estimated reciprocal transmission channel; and

    generating the first digital key from the properties of the estimated reciprocal transmission channel;

    wherein a direct signal component, transmitted on a direct signal path between the first communication device and the second communication device, of the first electromagnetic signal and of the second electromagnetic signal is attenuated;

    wherein the transmission channel between the first communication device and the second communication device is reciprocal when a time interval between a transmission of the first electromagnetic signal and transmission of the second electromagnetic signal is less than a coherence time of the transmission channel;

    wherein generating the first digital key and the second digital key further comprises;

    a quantisation step comprising comparing received electromagnetic signal values with one or more thresholds to determine a bit sequence from which each the digital key is calculated;

    orboth the quantisation step and an error correction step;

    wherein the properties of the estimated reciprocal transmission channel comprise;

    multi-path propagation, free space attenuation, shadowing, diffraction and absorption losses;

    utilizing the first digital key to encrypt communication from the first communication device to the second communication device;

    utilizing the second digital key to encrypt communication from the second communication device to the first communication device;

    wherein attenuation of the direct signal component is brought about by arranging part of a scattering object on the direct signal path; and

    wherein the scattering object has a conical or hemispherical or pyramid-shaped portion.

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