EAGER SARE: Physical-Layer Security of THz Communication Using Orbital Angular Momentum and Rapid Frequency Hopping

随着处理个人健康、财务和其他私人数据的无线设备数量的不断增长，与空中数据传输相关联的安全性成为主要关注点。目前，对数据传输的保护几乎完全依赖于数字加密，这存在各种弊端和漏洞。对于大容量数据传输，节能且快速的对称加密（例如，高级加密标准（AES）是常用的，但其密码密钥需要在发送器和接收器之间无线共享，容易被窃听。使用公钥基础设施的非对称加密（例如，RSA密码术）可用于确保密钥分发的安全，但它需要消耗能量的计算和复杂的双向通信协议。因此，使用无线硬件和电磁波的物理特性的附加非数字安全方法变得有吸引力。使用毫米波和太赫兹（THz）频率的窄光束传输有望减少窃听的机会。然而，由于实际天线阵列产生的固有非理想波束形状，信息泄漏仍然发生。为解决上述问题，本计画将研究一种新的安全无线传输密钥的方法的设计、分析与实验。预计将显著提高无线回程基础设施的能力，特别是未来的“超5G”网络，以防止窃听和攻击。该项目还将推进THz技术、微电子和无线安全领域的跨学科研究和教育。该项目将使用一种方案，将数据编码到各种空间分布模式（即，轨道角动量，OAM）的波前相位在太赫兹光束。这种方案的解码要求接收器沿OAM波的轴沿着精确定位，使得窃听非常困难并且易于被检测到。该项目将研究利用多种OAM模式叠加的方法，这进一步增强了安全性，并为非法接收者带来了额外的信息模糊性。为了避免任何可能的选择性干扰，还将应用比特级快速跳频方案。研究人员不仅将研究“类激光”传输方案在各种复杂黑客攻击场景下的理论安全性能极限，还将使用定制设计的微电子芯片进行实验演示。将执行THz OAM波的生成、检测、编码、跳频和波束控制等操作。该项目实现的单向、高安全性的密钥传输将补充现有的数字加密方案，并进一步了解太赫兹技术及其在无线安全系统中的应用。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the ever-growing number of wireless devices handling personal health, finance, and other private data, the security associated with the over-the-air data transmission becomes a major concern. At present, the protection of data transmission almost entirely relies on digital encryption, which has various drawbacks and vulnerabilities. For high-volume data transmission, energy-efficient and fast symmetric encryption (e.g., advanced encryption standard, AES) is commonly used, but its cipher secret key, which needs to be wirelessly shared between the transmitter and receiver, is susceptible to eavesdropping. Asymmetric encryption with a public-key infrastructure (e.g., RSA cryptography) can be used to secure key distribution, but it requires energy-consuming computation and complex two-way communication protocols. As a result, additional non-digital security approaches using the physical properties of wireless hardware and electromagnetic waves become attractive. Transmission using narrow beams at millimeter-wave and terahertz (THz) frequencies is expected to reduce the chance of eavesdropping. However, due to the inherently non-ideal beam shape generated by actual antenna arrays, leakage of information still occurs. To address the above issues, this project will investigate the design, analysis, and experiments of a new approach for secured wireless transmission of secret keys. It is expected to significantly increase the capabilities of wireless backhaul infrastructures, especially the future “beyond-5G” networks, against eavesdropping and attacking. It will also advance the interdisciplinary research and education across the fields of THz technologies, microelectronics, and wireless security.The project will use a scheme that encodes the data onto various spatial-distribution patterns (i.e., orbital-angular momentum, OAM) of the wave-front phases in a THz beam. The decoding of such a scheme requires the receiver to be precisely located along the axis of the OAM wave, making eavesdropping very hard and prone to be detected. The project will study approaches that utilize superposition of multiple OAM modes, which further enhances security with the additional information ambiguity induced to illegitimate receivers. To avoid any possible selective jamming, a bit-level rapid frequency hopping scheme will also be applied. The researchers will not only investigate the theoretical security performance limits of the “laser-like” transmission scheme against various sophisticated hacking scenarios, but also provide experimental demonstrations using custom-designed microelectronic chips. Operations such as the generation, detection, coding, frequency-hopping, and beam-steering of THz OAM waves will be performed. The one-way, high-security transmission of secret key to be enabled by this project will complement the existing digital encryption schemes and further the understanding of the THz technologies and applications in wireless security systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.