  We propose a novel advantage distillation strategy for physical layer-based
secret-key-agreement (SKA). We consider a scenario where Alice and Bob aim at
extracting a common bit sequence, which should remain secret to Eve, by
quantizing a random number obtained from measurements at their communication
channel. We propose an asymmetric advantage distillation protocol with two
novel features: i) Alice quantizes her measurement and sends partial
information on it over an authenticated public side channel, and ii) Bob
quantizes his measurement by exploiting the partial information. The partial
information on the position of the measurement in the quantization interval and
its sharing allows Bob to obtain a quantized value closer to that of Alice.
Both strategies increase the lower bound of the secret key rate.
