We consider block codes for degraded wiretap channels in which the legitimate receiver decodes the message with an asymptotic error probability ε but the leakage to the eavesdropper vanishes. For discrete memoryless and Gaussian wiretap channels, we show that the maximum rate of transmission does not depend on ε∈[0,1), i.e., such channels possess the partial strong converse property. Furthermore, we derive sufficient conditions for the partial strong converse property to hold for memoryless but non-stationary symmetric and degraded wiretap channels. Our proof techniques leverage the information spectrum method, which allows us to establish a necessary and sufficient condition for the partial strong converse to hold for general wiretap channels without any information stability assumptions.
more here.................http://arxiv.org/abs/1406.6758
more here.................http://arxiv.org/abs/1406.6758