Semi-Blind Key-Agreement Over MIMO Fading Channels
The authors analyze the fundamental limits of secret-key agreement over MIMO quasi-static fading channels. In the low-power and high-power regimes, they establish closed-form expressions for secret-key capacity. In the high-power regime, capacity is achieved with any transmission strategy that distributes power among all dimensions of the signal space. In the low-power regime, they show that the optimal signaling strategy is independent of the eavesdropper's fading realization. The low-power secret-key capacity is achieved by transmitting along the direction corresponding to the maximal eigenvalue of the legitimate channel.