Wiretap Channel with Side Information from Part of Encoder

The wiretap channel put forward by A.D. Wyner and the wiretap channel of type II provided by A.D. Wyner and L. H. Oz arow play important roles in network communication and security. In this paper, we consider the situation that a wiretapper can not only tap the main channel output via a noisy wiretap channel, but also get someside information from part of encoder, i.e., some transmitted symbols of the output of the encoder. In other words, the new model of this paper is a combination of the wiretap channel and the wiretap channel of type II. The new model of this paper is different from I. Csiszar and J. Korner ´s model [CK], it is also different from N. Merhav´s model [Me]. A single-letter characterization is provided for a region composed of all achievable triples: the equivocation to the wiretapper, the reliable transmission rate of the main channel, the ratio of the leaked transmitted symbols. In particular, if the equivocation to the wiretapper is equal to the entropy of the data symbols, then we say that the transmission is accomplished in perfect secrecy. Our results imply in which cases (of the ratio of the leaked transmitted symbols), there may exist a C´_s>0, such that reliable transmission at rates up to C´_s is in perfect secrecy.