Matched Information Rate Codes for Binary-Input Intersymbol Interference Wiretap Channels

A two-stage coding scheme is proposed for reliable and secure transmission over intersymbol interference wiretap channels (ISI-WTCs). It is shown that the ultimate bound on the secure rate of linear block codes over ISI-WTCs is achieved by an independent and uniformly distributed (i.u.d.) input process. Aiming to exceed the i.u.d. secure rate, the proposed scheme comprises the concatenation of an inner trellis code and an outer coset code. The inner stage emulates a Markov process for achieving the constrained secrecy capacity of the ISI-WTC. In contrast, the outer stage vanishes an obtained upper bound on the rate of information leakage toward satisfying the so-called weak secrecy criterion. A carefully modified density evolution confirms the secrecy and the reliability efficiency of the proposed coding scheme at secure rates close to the constrained secrecy capacity.