We propose a two-stage concatenated coding scheme for reliable and secure communication over intersymbol interference wiretap channels. We first establish the secrecy capacity. Then, motivated by the theoretical codes that achieve the secrecy capacity, our scheme integrates low-density parity-check (LDPC) codes in the outer stage, forming a nested structure of wiretap codes, with trellis codes in the inner stage to improve achievable secure rates. The trellis code is specifically designed to transform the uniformly distributed codewords produced by the LDPC code stage into a Markov process, achieving tight lower bounds on the secrecy capacity. We further estimate the information leakage rate of the proposed scheme using an upper bound. To meet the weak secrecy criterion, we optimize degree distributions of the irregular LDPC codes at the outer stage, essentially driving the estimated upper bound on the information leakage rate to zero.

翻译：我们提出了一种两阶段级联编码方案，用于在符号间干扰窃听信道上实现可靠且安全的通信。首先建立了保密容量。随后，受能够达到保密容量的理论编码启发，该方案在外层阶段集成了低密度奇偶校验（LDPC）码，形成窃听码的嵌套结构，内层阶段采用网格码以提高可达安全速率。网格码经过专门设计，将LDPC码阶段产生的均匀分布码字转化为马尔可夫过程，从而逼近保密容量的严格下界。进一步利用上界估计了所提方案的信息泄漏率。为满足弱保密准则，我们优化了外层不规则LDPC码的度分布，使得信息泄漏率的估计上界趋近于零。