Strong Converse for a Degraded Wiretap Channel via Active Hypothesis   Testing
  We establish an upper bound on the rate of codes for a wiretap channel with public feedback for a fixed probability of error and secrecy parameter. As a corollary, we obtain a strong converse for the capacity of a degraded wiretap channel with public feedback. Our converse proof is based on a reduction of active hypothesis testing for discriminating between two channels to coding for wiretap channel with feedback. 
Masahito Hayashi, Himanshu Tyagi, Shun Watanabe
cs.IT math.IT