We study the secret-key capacity of a non-coherent, two-way, block-fading
wireless channel. We assume that the channel gains in the forward and reverse
links are correlated. We establish upper and lower bounds on the secret-key
capacity that coincide in certain regimes. Our lower bound uses part of each
coherence block for transmitting training symbols and the remainder of the
coherence block for randomness-exchange. In general, our proposed technique
significantly improves upon the rate achieved by training-only schemes, widely
used in the literature.