Security and eavesdropping in terahertz wireless links
Security and eavesdropping in terahertz wireless links
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DOI：
10.1038/s41586-018-0609-x
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发表时间：
2018-11-01
期刊：
影响因子：
64.8
通讯作者：
Mittleman, Daniel M.
中科院分区：
文献类型：
--
作者：
Ma, Jianjun;Shrestha, Rabi;Mittleman, Daniel M.
针对窃听和其他安全威胁的弹性已成为通信系统设计的关键考虑因素之一。随着无线系统变得无处不在，对各级安全协议的需求越来越大，包括软件（如加密）、硬件（如可信平台模块）和物理层（如波前工程）（1-5）。随着不可避免地向更高的载波频率转移，特别是在太赫兹范围内（100千兆赫以上），一个重要的考虑是由于衍射对波长较短的波的影响减少，发射信号的角散度减少（即方向性增加）。近年来，对以太赫兹频率工作的无线设备（6-8）和系统（9-11）的研究显著增加。与使用较低频率的广域广播相比，这些高频窄角度广播对窃听者来说更具挑战性（12,13）。然而，尽管人们普遍认为高频无线数据链路的安全性得到了提高（14-16），但太赫兹窃听的可能性尚未得到表征。最近的一些研究考虑了较低频率（5,12,13,17,18）的问题，但通常认为窃听者的天线必须位于发射天线的广播扇区内，从而得出结论，当发射信号具有足够高的方向性时，窃听基本上是不可能的（15）。在这里，我们证明，与这种期望相反，窃听者可以拦截视线传输中的信号，即使它们是以窄波束的高频传输。窃听者的技术与低频传输的技术不同，因为它们涉及在传输路径上放置一个物体，以向窃听者散射辐射。我们还讨论了这种窃听技术的一种对抗措施，该措施涉及表征信道的后向散射。我们表明，这种反措施可以用来检测一些，虽然不是全部，窃听者。我们的工作强调了太赫兹无线网络中物理层安全的重要性，以及对包含新对策的收发器设计的需求。
Resiliency against eavesdropping and other security threats has become one of the key design considerations for communication systems. As wireless systems become ubiquitous, there is an increasing need for security protocols at all levels, including software (such as encryption), hardware (such as trusted platform modules) and the physical layer (such as wave-front engineering)(1-5). With the inevitable shift to higher carrier frequencies, especially in the terahertz range (above 100 gigahertz), an important consideration is the decreased angular divergence (that is, the increased directionality) of transmitted signals, owing to the reduced effects of diffraction on waves with shorter wavelengths. In recent years, research on wireless devices(6-8) and systems(9-11) that operate at terahertz frequencies has ramped up markedly. These high-frequency, narrow-angle broadcasts present a more challenging environment for eavesdroppers compared to the wide-area broadcasts used at lower frequencies(12,13). However, despite the widespread assumption of improved security for high-frequency wireless data links(14-16), the possibility of terahertz eavesdropping has not yet been characterized. A few recent studies have considered the issue at lower frequencies(5,12,13,17,18), but generally with the idea that the eavesdropper's antenna must be located within the broadcast sector of the transmitting antenna, leading to the conclusion that eavesdropping becomes essentially impossible when the transmitted signal has sufficiently high directionality(15). Here we demonstrate that, contrary to this expectation, an eavesdropper can intercept signals in line-of-sight transmissions, even when they are transmitted at high frequencies with narrow beams. The eavesdropper's techniques are different from those for lower-frequency transmissions, as they involve placing an object in the path of the transmission to scatter radiation towards the eavesdropper. We also discuss one counter-measure for this eavesdropping technique, which involves characterizing the backscatter of the channel. We show that this counter-measure can be used to detect some, although not all, eavesdroppers. Our work highlights the importance of physical-layer security in terahertz wireless networks and the need for transceiver designs that incorporate new counter-measures.