Secret-key generation from wireless channels: Mind the reflections

We study the problem of secret-key generation in a wireless environment by exploiting the inherent randomness and reciprocity of the channel gain. A channel model is proposed which takes into account the effect of reflections (or re-radiations) from receive antenna elements, thus capturing a physical property of practical antennas. It turns out that the reflections have a deteriorating effect on the achievable secret-key rate at high signal-to-noise ratio (SNR). These insights provide guidelines in the design and operation of communication systems using the properties of the wireless channel to prevent eavesdropping.