Establishing secure links between wireless devices in proximity using ambient wireless signals

摘要

Wireless devices in proximity are securely paired with one another autonomously by generating a common cryptographic key directly from a time-varying wireless environment shared among the wireless devices. The shared key can be used by the wireless devices to authenticate each wireless device's physical proximity and then to facilitate confidential communication between the wireless devices. The algorithm used to create the shared key is secure against a computationally unbounded adversary and its computational complexity is linear in the size of the shared key.

主权项

1. A method for establishing secure links between devices, the method comprising:
obtaining measurements of a wireless channel at a first wireless device that is within a proximity of a second wireless device; calculating a coherence time (Tc) of the wireless channel using the measurements; determining relative minima and relative maxima in the measurements;separating each successive one of the relative minima and the relative maxima by the coherence time;
determining a time index at which each of the relative minima and the relative maxima occurs; creating a list of time indices comprising the time index at which each of the relative minima and the relative maxima occurs; extracting a first bit sequence from the measurements of the wireless channel; wherein obtaining the measurements of the wireless channel comprises sampling an ambient wireless signal from a source and obtaining the measurements using a sample derived from the sampling, and wherein extracting the first bit sequence from the measurements comprises demodulating the ambient wireless signal using the sample to derive a demodulated signal; sending the list of time indices and a code-offset with respect to an error-correcting code to the second wireless device over an insecure connection between the first wireless device and the second wireless device, the error-correcting code being known to the first wireless device and the second wireless device prior to the code-offset being sent; and establishing a secure link between the first wireless device and the second wireless device using the first bit sequence as a shared key, the first bit sequence being known to the second wireless device based upon the second wireless device using the list of time indices, the code-offset, the error-correcting code, and a second bit sequence extracted by the second wireless device to derive the first bit sequence as the shared key.