Strong secrecy communication over a discrete memoryless state-dependent multiple access channel (SD-MAC) with an external eavesdropper is investigated. The channel is governed by discrete memoryless and i.i.d. channel states and the channel state information (CSI) is revealed to the encoders in a causal manner. Inner and outer bounds are provided. To establish the inner bound, we investigate coding schemes incorporating wiretap coding and secret key agreement between the sender and the legitimate receiver. Two kinds of block Markov coding schemes are proposed. The first one is a new coding scheme using backward decoding and Wyner-Ziv coding and the secret key is constructed from a lossy description of the CSI. The other one is an extended version of the existing coding scheme for point-to-point wiretap channels with causal CSI. A numerical example shows that the achievable region given by the first coding scheme can be strictly larger than the second one. However, these two schemes do not outperform each other in general and there exists some numerical examples that in different channel models each coding scheme achieves some rate pairs that cannot be achieved by another scheme. Our established inner bound reduces to some best-known results in the literature as special cases. We further investigate some capacity-achieving cases for state-dependent multiple access wiretap channels (SD-MAWCs) with degraded message sets. It turns out that the two coding schemes are both optimal in these cases.

翻译：本文研究了存在外部窃听者时，在离散无记忆状态依赖多址接入信道（SD-MAC）上实现强保密通信的问题。该信道受离散无记忆且独立同分布的信道状态支配，且信道状态信息（CSI）以因果方式提供给编码器。我们给出了内外界界。为建立内界，我们研究了结合窃听编码和发送方与合法接收方之间密钥协商的编码方案，并提出了两种块马尔可夫编码方案。第一种方案采用后向译码和Wyner-Ziv编码的新颖编码方案，密钥由CSI的有损描述构建；第二种方案是现有针对具有因果CSI的点对点窃听信道编码方案的扩展版本。数值示例表明，第一种编码方案可达的区域严格大于第二种。然而，这两种方案在一般情况下互不占优，存在数值示例显示不同信道模型中每种编码方案都能实现对方无法达到的某些速率对。我们建立的内界在特殊情形下可退化为文献中若干已知最优结果。我们进一步研究了具有降级消息集的SD-MAWC（状态依赖多址接入窃听信道）的容量可达情形，发现这两种编码方案在这些情形下均为最优。