An apparatus includes a first transceiver, at least two antennas coupled to the first transceiver to exchange one or more keys and phase data with a second transceiver via a plurality of rounds of phase data exchange, each round including: a first pilot signal sent from a first of the antennas of the first transceiver to the second transceiver, a second pilot signal received from the second transceiver, the second pilot signal modulated using a measured first phase of the first pilot signal, a third pilot signal received from the second transceiver; a fourth pilot signal sent from a second of the antennas of the first transceiver to the second transceiver, the fourth pilot signal modulated using a measured second phase of the third pilot signal, and wherein between the plurality of rounds of phase exchange, the first transceiver perturbs a radio frequency (RF) environment surrounding the at least two antennas.