New Problems Of Wiretap Channel And Wiretap Channel Of Type II

The wiretap channel and the wiretap channel of type II put forward byWyner have been widely studied by many researchers. In this paper, there aretwo new problems in the above models. One problem is that the wiretapper in thewiretap channel can not only view the channel output via a second noisy channel,but also can get some side information about the symbols that transmitted in themain noisy channel. The designer tries to build an encoder-decoder in such a wayas to maximize the transmission rate R, and the equivocation d of the informationas seen by the wiretapper.We find a regionΨwhich is composed of all achievable(R,d) pairs. In particular, if d is equal to Hs, the entropy of the data source, thenwe consider that the transmission is accomplished in perfect secrecy.Our resultimplies that there exists a Cs > 0, such that reliable transmission at rates up toCs is possible in perfect secrecy. The other problem is how to improve the resultof the model of wiretap channel of type II. By using a new coding and decodingscheme on the model of wiretap channel of type II, the result of the model hasbeen greatly improved. Finally, we have studied the maximum transmission rateswhen prefect secrecy is achieved in the wiretap channel and the wiretap channelof type II, these rates are also called"secrecy capacity"by Wyner, it is the mostimportant parameter in the above models.