In this paper we consider a wiretap channel II with an active eavesdropper. Aggarwal et al (2009) were the first who studied the Ozarow-Wyner's binary wiretap channel II in the presence of an active eavesdropper. They derived achievable secrecy rates for two modification models where the eavesdropper can erase/replace the bits he observes. The existence of better achievable rates remains an open problem. Here we study a model with a less powerful eavesdropper. The eavesdropper is able now to observe any interval of μ symbol positions and erase the symbols in any interval of l positions of a transmitted codeword. We present an explicit construction of nested linear codes that achieve maximum secrecy rate for the finite length coding regime, with perfect secrecy and zero-error decoding, for any admissible code parameters.
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