An alternative proof for the secrecy capacity region of the Gaussian wiretap channel

This paper considers the problem of proof for the secrecy capacity region of the Gaussian wiretap channel. In this channel, the transmitter sends confidential messages to the legitimate receivers, which need to be kept asymptotically perfectly secret from the eavesdropper. We characterize the secrecy capacity region of this channel and give a converse proof by using the fundamental relationship between information theory and the estimation theory in the Gaussian channel, relating the derivative of the mutual information to the minimum mean-square-error (MMSE). Our proof is different from the superposition coding and the random binning. We obtain that using the relationship between MMSE and mutual information one can provide insightful and simple proofs for multiuser single antenna problems and the secrecy capacity problem, such as broadcast channel.