<p>The last few decades have witnessed unprecedented growth in multiple areas of electronics spanning low-power sensing, intelligent computing and high-speed wireless connectivity. In the foreseeable future, there would be hundreds of billions of computing devices, sensors, things and people, wherein the technology will become intertwined with our lives through continuous interaction and collaboration between humans and machines. Such human-centric ideas give rise to the concept of internet of bodies (IoB), which calls for novel and energy-efficient techniques for sensing, processing and secure communication for resource-constrained IoB nodes.As we have painfully learnt during the pandemic, point-of-care diagnostics along with continuous sensing and long-term connectivity has become one of the major requirements in the healthcare industry, further emphasizing the need for energy-efficiency and security in the resource-constrained devices around us.</p> <p>  </p> <p>  With this vision in mind, I’ll divide this dissertation into the following chapters. The first part (Chapter 2) will cover time-domain sensing techniques which allow inherent energy-resolution scalability, and will show the fundamental limits of achievable resolution. Implementations will include 1) a radiation sensing system for occupational dosimetry in healthcare and mining applications, which can achieve 12-18 bit resolution with 0.01-1 µJ energy dissipation, and 2) an ADC-less neural signal acquisition system with direct Analog to Time Conversion at 13pJ/Sample. The second part (Chapters 3 and 4) of this dissertation will involve the fundamentals of developing secure energy-efficient electro-quasistatic (EQS) communication techniques for IoB wearables as well as implants, and will demonstrate  2 examples: 1) Adiabatic Switching for breaking the αCV^2f limit of power consumption in capacitive voltage mode human-body communication (HBC), and 2) Bi-Phasic Quasistatic Brain Communication (BP-QBC) for fully wireless data transfer from a sub-6mm^3, 2 µW brain implant. A custom modulation scheme, along with adiabatic communication enables wireline-like energy efficiencies (<5pJ/b) in HBC-based wireless systems, while the BP-QBC node, being fully electrical in nature, demonstrates sub-50pJ/b efficiencies by eliminating DC power consumption, and by avoiding the transduction losses observed in competing technologies, involving optical, ultrasound and magneto-electric modalities. Next in Chapter 5, we will show an implementation of a reconfigurable system that would include 1) a human-body communication transceiver and 2) a traditional wireless (MedRadio) transceiver on the same integrated circuit (IC), and would demonstrate methods to switch between the two modes by detecting the placement of the transmitter and receiver devices (on-body/away from the body). Finally, in Chapter 6, we shall show a technique of augmenting security in resource-constrained devices through authentication using the Analog/RF properties of the transmitter, which are usually discarded as non-idealities in a digital transceiver chain. This method does not require any additional hardware in the transmitter, making it an extremely promising technique to augment security in highly resource-constrained scenarios. Such energy-efficient intelligent sensing and secure communication techniques, when combined with intelligent in-sensor-analytics at the resource-constrained nodes, can potentially pave the way for perpetual, and even batteryless systems for next-generation IoT, IoB and healthcare applications.</p>

<p dir="ltr">Unintentional electromagnetic emission (called emanation) from electronic devices and cables contains a significant correlation with the source signal and can be used to recover otherwise confidential data. In our work, EM emanation has been exploited to recover keystrokes from USB keyboards. Also, such emission has been utilized to form a covert channel for data exfiltration from air-gapped devices without being detected by IDS. To protect sensitive information, an automated emanation detection system has been proposed by developing two emanation detection algorithms (CNN-based and harmonic-based) through the characterization of emanation signals from a wide range of devices. Apart from emanation, data theft can happen due to the failure of access control methods. Traditional wireless devices are susceptible to various spoofing attacks as they only use digital signature-based authentication systems, ignoring the physical signatures completely. To circumvent that, RF-PUF was proposed to use device-specific signatures to be used for trust augmentation in traditional methods. By forming an extensive experimental dataset, we established RF-PUF as a strong PUF with a low-power overhead that outperformed the state-of-the-art methods and is robust against typical attacks. For real-time authentication, we proposed DIRAC, which forms dynamic device clusters and incrementally learns as more device data becomes available. Since our root of trust is in the physical signature of the ICs, they also need to be secured. However, counterfeited ICs may jeopardize that goal. We have proposed RF-PSF, which uses device-specific physical properties to authenticate its process technology which is a big part of the cloned IC detection.</p>