Free-space optical secret key agreement with post-selection based on channel state information
Free-space optical secret key agreement with post-selection based on channel state information
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DOI：
10.1117/12.2532232
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发表时间：
2019-10
期刊：
影响因子：
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通讯作者：
H. Endo;M. Fujiwara;M. Kitamura;O. Tsuzuki;R. Shimizu;M. Takeoka;M. Sasaki
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文献类型：
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作者：
H. Endo;M. Fujiwara;M. Kitamura;O. Tsuzuki;R. Shimizu;M. Takeoka;M. Sasaki
自由空间光通信（FSO）因其丰富的高频特性而成为大容量无线通信的重要手段。这些特点也产生了更大的安全优势，超过无线电频率同行：物理能力的窃听是合理的限制，由于高方向性的通信波束和视线配置的链接。FSO链路上的密钥协商（FSO-SKA）利用了这一安全优势，并通过认证公共信道进行后处理，建立了一个信息论安全密钥，即使在无限的计算机资源下也不能被破解。在以前的工作中，作者展示了FSO-SKA的全场实现，其中包括一个7.8公里的FSO链路测试平台，包括一个探测站，以估计通信波束旁瓣可能的窃听风险。然而，在演示中，仍然有空间来提高密钥速率，通过利用光衰落，其中包含有关FSO链路的随机状态的附加信息。在这里，我们提出了一种新的协议FSO-SKA采用这样的信道状态信息。在该协议中，合法接收机根据接收时的光功率决定是否丢弃接收到的符号。基于FSO链路测试平台的实验数据，我们证明了所提出的协议与我们以前的结果相比，提高了密钥速率。据我们所知，这是第一次利用大气干扰的影响来提高通信系统的安全性能。我们期望这个想法将适用于更广泛的领域的FSO通信，并开辟了一条道路，走向实用的无线网络跨越的FSO链路。
Free-space optical (FSO) communications are becoming promising schemes for high-capacity wireless links due to their plentiful characteristics originated from higher carrier frequency. These characteristics also yield a greater security advantage over radio frequency counterparts: the physical ability of a wiretapper is reasonably restricted due to the high directionality of communication beam and the line-of-sight configuration of the link. Secret key agreement over FSO links (FSO-SKA) employs this security advantage as well as the post-processing over an authenticated public channel to establish an information-theoretic secure key which cannot be broken even with unbounded computer resources. In the previous works, the authors demonstrated the full-field implementations of FSO-SKA with a 7.8-km FSO link testbed including a probing station to estimate the possible wiretapping risks from the sidelobe of the communication beam. In the demonstration, however, there is still room to improve the secret key rate by exploiting the optical fading which contains additional information about random states of the FSO links. We here propose a novel protocol for FSO-SKA employing such channel state information. In the protocol, the legitimate receiver decides whether to discard the received symbols or not according to the received optical power at the time. Based on the experimental data from the FSO link testbed, we demonstrate that the proposed protocol improves the secret key rate compared with our previous result. To our best knowledge, this is the first demonstration that exploits the effect of atmospheric turbulences to improve the security performance of communication systems. We anticipate that this idea will be applicable on the broader areas of FSO communications and opens a way toward practical wireless network spanned by FSO links.