Time Correlation Analysis of Secret Key Generation via UWB Channels

Wireless channel characterization is a known methodology for the generation of secret keys, where the secrecy of the key depends on the spatial-temporal correlation properties of the channel which themselves arise due to the channel´s physical constraints. Spatial correlations can be suitably addressed simply by moving from narrow band channels to ultra-wide band (UWB) channels, but this does not address temporal correlations, (i.e., the likelihood that two successive key generation processes will generate the same, or nearly the same, key). This work shows that the worst-case of the temporal correlation problem, (i.e., when an eavesdropper has perfect knowledge of all past channel characterizations) is effectively addressed by applying channel prediction to the available ensemble of channel characterisation events and removing the predictable ensembles. It is shown that this proposed prediction approach increases the security of the key generation process while simultaneously reduce the available amount of information for the key generation. Moreover, real-world experimental data is also applied to confirm that a linear prediction suffices in this case.