EAGER: SARE: Directional Modulation Non-Contiguous OFDM Retrodirective Communication for Secure IoT

在即将到来的物联网(IoT)时代，数十亿台物理设备将联网在一起，并支持智能家居和智能城市等新兴概念，从而带来互联人类社会的新范式。因此，智能传感器和控制器等设备-通常使用小容量电池运行，在超低功耗处理器上运行应用-将需要能够在连接到互联网云的同时相互通信。在这种情况下，物联网网关是连接物联网设备和互联网的重要组件。由于物联网网关将需要在边缘物联网设备上处理关键任务，因此确保网关和设备之间的安全通信链路以防止敌对实体的任何欺骗性攻击至关重要。由于边缘设备和网关之间的端到端加密会话由于这种加密策略的高计算资源需求和电池负担而不能被依赖于安全通信，因此迫切需要开发物理层(PHY)安全通信方案。为此，本项目开发了一种定向调制非邻接正交频分复用(NC-ofdm)反向通信方案，将对物联网应用的安全产生深远影响。该项目的成果将使物联网设备和网关之间能够实现高度安全的PHY通信方案，以抵御恶意欺骗攻击。此外，NC-OFDM和定向调制反向定向阵列的独特组合将使此类攻击即使使用复杂的机器学习(ML)技术也不太可能成功。此外，该项目的教育计划旨在扩大研究生、本科生和高中生，包括代表性不足的少数群体，参与微波和天线技术、信号处理和ML以及无线通信的相关研究。在技术细节方面，该研究项目解决了物联网应用中的一个关键安全问题，该应用通过结合NC-ofdm传输和定向调制反向定向阵列的创新物理层解决方案，容易受到恶意欺骗攻击。与传统的ofdm传输相比，NC-ofdm传输在活动子载波子集上进行，以避免现有传输或出于战略考虑。因此，NC-ofdm传输具有低概率利用基于循环平稳分析的经典攻击的特性。另一方面，众所周知，反向天线阵列能够通过在没有先验知识的情况下将信号发送回询问器位置来响应询问器，这在多径丰富的环境中特别有用。通过结合定向调制技术，天线阵列将通过在所有不想要的发射方向上扭曲数字调制的星座图来破坏信息。实现定向调制功能的一种方式是使用时间调制天线阵列，其中时间调制频率产生的混叠效应被用来使信号在不希望的方向上失真。此外，由调制频率为NC-OFDM子载波的时间调制反向天线阵列实现的NC-ofdm和定向调制的独特集成可能会潜在地导致针对对手的欺骗攻击的PHY硬件安全达到前所未有的水平，即使对手配备了复杂的基于ML的攻击技术。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In the upcoming era of the Internet-of-Things (IoT), billions of physical devices will be networked together and enable emerging concepts, such as smart homes and smart cities, leading to new paradigms for connected human societies. As such, devices such as intelligent sensors and controllers—often operating on small-capacity batteries and running applications on ultra-low-power processors—will need to be able to communicate with each other, while being connected to the internet cloud. In this scenario, IoT gateways serve as an essential component in bridging IoT devices and the internet. As the IoT gateways will need to deal with critical tasks at the edge IoT devices, it is essential to ensure secure communication links between the gateway and the devices against any spoofing attacks by adversarial entities. Since end-to-end encrypted sessions between the edge devices and the gateway cannot be relied upon for secure communications due to the high computational resource demand and battery burden of such cryptographic strategies, there is an urgent need to develop physical-layer (PHY) secure communication schemes. To this end, this project develops a directional modulation non-contiguous orthogonal frequency division multiplexing (NC-OFDM) retrodirective communication scheme that will have a profound impact in securing IoT applications. The outcome of this project will enable a highly secure PHY communication scheme among the IoT devices and gateways against malicious spoofing attacks. Furthermore, the unique combination of NC-OFDM and directional modulation retrodirective array will make such attacks very unlikely to succeed even with sophisticated machine learning (ML) techniques. In addition, the educational plan of the project aims to broaden participation of graduate, undergraduate and high school students, including underrepresented minority groups, in relevant research on microwave and antenna technologies, signal processing and ML, and wireless communications.In terms of technical details, the research project addresses a critical security issue in IoT applications that are susceptible to malicious spoofing attacks via an innovative PHY solution combining NC-OFDM transmission and a directional modulation retrodirective array. As compared with traditional OFDM transmissions, NC-OFDM transmissions take place over a subset of active subcarriers to either avoid incumbent transmissions or for strategic considerations. As such, NC-OFDM transmissions have low probability of exploitation characteristics against classic attacks based on cyclostationary analysis. On the other hand, retrodirective antenna arrays are well known to be able to respond to an interrogator by sending signals back to the interrogator location without a priori knowledge, which is particularly useful in a multipath-rich environment. By incorporating the directional modulation technique, the antenna array will corrupt the information by distorting the digital modulation’s constellation diagrams in all unwanted transmitting directions. One way to realize the directional modulation functionality is to use time-modulated antenna arrays, in which the aliasing effects resulting from the time-modulation frequency are used to distort the signals in the undesired directions. Furthermore, the unique integration of NC-OFDM and directional modulation enabled by a time-modulated retrodirective antenna array whose modulation frequency is the NC-OFDM subcarrier can potentially lead to an unprecedented level of PHY hardware security against spoofing attacks by an adversary, even when the adversary is equipped with sophisticated ML-based attack techniques.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.