In this work, we focus on the classical optical channel having Poissonian statistical behavior and propose a novel secrecy coding-based physical layer protocol. Our protocol is different but complementary to both (computationally secure) quantum immune cryptographic protocols and (information theoretically secure) quantum cryptographic protocols. Specifically, our (information theoretical) secrecy coding protocol secures classical digital information bits at photonic level exploiting the random nature of the Poisson channel. It is known that secrecy coding techniques for the Poisson channel based on the classical one-way wiretap channel (introduced by Wyner in 1975) ensure secret communication only if the mutual information to the eavesdropper is smaller than that to the legitimate receiver. In order to overcome such a strong limitation, we introduce a two-way protocol that always ensures secret communication independently of the conditions of legitimate and eavesdropper channels. We prove this claim showing rigorous comparative derivation and analysis of the information theoretical secrecy capacity of the classical one-way and of the proposed two-way protocols. We also show numerical calculations that prove drastic gains and strong practical potential of our proposed two-way protocol to secure information transmission over optical channels.

中文翻译：

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泊松通道的物理层安全协议，用于被动中间人攻击

在这项工作中，我们将重点放在具有泊松统计行为的经典光信道上，并提出一种新颖的基于保密编码的物理层协议。我们的协议是不同的，但对（计算上安全的）量子免疫密码协议和（信息上理论上的安全）量子密码协议都是互补的。具体来说，我们的（信息理论上的）保密编码协议利用泊松信道的随机特性在光子级确保了经典的数字信息位。众所周知，基于经典单向窃听信道的Poisson信道的保密编码技术（由Wyner于1975年提出）仅在窃听者的共同信息小于合法接收者的共同信息时才确保秘密通信。为了克服这种强大的限制，我们引入了一种双向协议，该协议始终确保独立于合法和窃听者渠道的情况下的秘密通信。我们证明了这种说法，它显示了对经典单向协议和提议的双向协议的信息理论保密能力的严格比较推导和分析。我们还显示了数值计算，这些数值计算证明了我们提出的双向协议可确保通过光信道传输信息的巨大收益和强大的实践潜力。