Strong and weak secrecy in wiretap channels

In the wiretap channel model, symbols transmitted through a main channel to a legitimate receiver are observed by an eavesdropper across a wiretapper´s channel. The goal of coding for wiretap channels is to facilitate error-free decoding across the main channel, while ensuring zero information transfer across the wiretapper´s channel. Strong secrecy requires the total information transfer to the eavesdropper to tend to zero, while weak secrecy requires the per-symbol information transfer to go to zero. In this paper, we will consider coding methods for binary wiretap channels with a noiseless main channel and a BEC or a BSC wiretapper´s channel. We will provide conditions and codes that achieve strong and weak secrecy for the BEC case. For the BSC case, we will discuss some existing coding methods and develop additional criteria for secrecy.