Forward Reconciliation for Covert Key Generation

We propose a forward reconciliation algorithm for covert key generation based on pulse-position modulation (PPM) and multilevel coding (MLC) with multistage decoding (MSD). This multilevel scheme not only allows one to concentrate the diffuse information content of the sparse signals used for covertness but also enables the use of independent codes at each level designed for stationary channels. In particular, we show that polar codes offer a low-complexity reconciliation-capacity achieving solution.