Wiretap channel with shared key

This paper studies the problem of secure communication over a wiretap channel where the transmitter and the legitimate receiver share a secret key, which is concealed from the eavesdropper. We find the secrecy capacity under this scenario. This result generalizes that of Yamamoto, which is applicable only to less noisy wiretap channels, to the general wiretap channel when no distortion is allowed at the legitimate receiver.