Sensor networks with battery-powered nodes can seldom simultaneously meet the design goals of lifetime, cost, sensing reliability and sensing and transmission coverage. Energy-harvesting, converting ambient energy to electrical energy, has emerged as an alternative to power sensor nodes. By exploiting recharge opportunities and tuning performance parameters based on current and expected energy levels, energy harvesting sensor nodes have the potential to address the conflicting design goals of lifetime and performance. This paper surveys various aspects of energy harvesting sensor systems- architecture, energy sources and storage technologies and examples of harvesting-based nodes and applications. The study also discusses the implications of recharge opportunities on sensor node operation and design of sensor network solutions.

Energy Harvesting Sensor Nodes: Survey and Implications

The most visible use of computers and software is processing information for human consumption. The vast majority of computers in use, however, are much less visible. They run the engine, brakes, seatbelts, airbag, and audio system in your car. They digitally encode your voice and construct a radio signal to send it from your cell phone to a base station. They command robots on a factory floor, power generation in a power plant, processes in a chemical plant, and traffic lights in a city. These less visible computers are called embedded systems, and the software they run is called embedded software. The principal challenges in designing and analyzing embedded systems stem from their interaction with physical processes. This book takes a cyber-physical approach to embedded systems, introducing the engineering concepts underlying embedded systems as a technology and as a subject of study. The focus is on modeling, design, and analysis of cyber-physical systems, which integrate computation, networking, and physical processes. The second edition offers two new chapters, several new exercises, and other improvements. The book can be used as a textbook at the advanced undergraduate or introductory graduate level and as a professional reference for practicing engineers and computer scientists. Readers should have some familiarity with machine structures, computer programming, basic discrete mathematics and algorithms, and signals and systems.

Introduction to Embedded Systems - A Cyber-Physical Systems Approach

Intermittently powered applications create a need for low-cost security and privacy in potentially hostile environments, supported by primitives including identification and random number generation. Our measurements show that power-up of SRAM produces a physical fingerprint. We propose a system of fingerprint extraction and random numbers in SRAM (FERNS) that harvests static identity and randomness from existing volatile CMOS memory without requiring any dedicated circuitry. The identity results from manufacture-time physically random device threshold voltage mismatch, and the random numbers result from runtime physically random noise. We use experimental data from high-performance SRAM chips and the embedded SRAM of the WISP UHF RFID tag to validate the principles behind FERNS. For the SRAM chip, we demonstrate that 8-byte fingerprints can uniquely identify circuits among a population of 5,120 instances and extrapolate that 24-byte fingerprints would uniquely identify all instances ever produced. Using a smaller population, we demonstrate similar identifying ability from the embedded SRAM. In addition to identification, we show that SRAM fingerprints capture noise, enabling true random number generation. We demonstrate that a 512-byte SRAM fingerprint contains sufficient entropy to generate 128-bit true random numbers and that the generated numbers pass the NIST tests for runs, approximate entropy, and block frequency.

Power-Up SRAM State as an Identifying Fingerprint and Source of True Random Numbers

Internet-of-Things (IoT) are everywhere in our daily life. They are used in our homes, in hospitals, deployed outside to control and report the changes in environment, prevent fires, and many more beneficial functionality. However, all those benefits can come of huge risks of privacy loss and security issues. To secure the IoT devices, many research works have been conducted to countermeasure those problems and find a better way to eliminate those risks, or at least minimize their effects on the user’s privacy and security requirements. The survey consists of four segments. The first segment will explore the most relevant limitations of IoT devices and their solutions. The second one will present the classification of IoT attacks. The next segment will focus on the mechanisms and architectures for authentication and access control. The last segment will analyze the security issues in different layers.

A Survey on Security and Privacy Issues in Internet-of-Things

With the exponential growth of cyber-physical systems (CPSs), new security challenges have emerged. Various vulnerabilities, threats, attacks, and controls have been introduced for the new generation of CPS. However, there lacks a systematic review of the CPS security literature. In particular, the heterogeneity of CPS components and the diversity of CPS systems have made it difficult to study the problem with one generalized model. In this paper, we study and systematize existing research on CPS security under a unified framework. The framework consists of three orthogonal coordinates: 1) from the security perspective, we follow the well-known taxonomy of threats, vulnerabilities, attacks and controls; 2) from the CPS components perspective, we focus on cyber, physical, and cyber-physical components; and 3) from the CPS systems perspective, we explore general CPS features as well as representative systems (e.g., smart grids, medical CPS, and smart cars). The model can be both abstract to show general interactions of components in a CPS application, and specific to capture any details when needed. By doing so, we aim to build a model that is abstract enough to be applicable to various heterogeneous CPS applications; and to gain a modular view of the tightly coupled CPS components. Such abstract decoupling makes it possible to gain a systematic understanding of CPS security, and to highlight the potential sources of attacks and ways of protection. With this intensive literature review, we attempt to summarize the state-of-the-art on CPS security, provide researchers with a comprehensive list of references, and also encourage the audience to further explore this emerging field.

https://ieeexplore.ieee.org/ielaam/6488907/8172502/7924372-aam.pdf

Cyber-Physical Systems Security—A Survey

Our study analyzes the security and privacy properties of an implantable cardioverter defibrillator (ICD). Introduced to the U.S. market in 2003, this model of ICD includes pacemaker technology and is designed to communicate wirelessly with a nearby external programmer in the 175 kHz frequency range. After partially reverse-engineering the ICD's communications protocol with an oscilloscope and a software radio, we implemented several software radio-based attacks that could compromise patient safety and patient privacy. Motivated by our desire to improve patient safety, and mindful of conventional trade-offs between security and power consumption for resource-constrained devices, we introduce three new zero-power defenses based on RF power harvesting. Two of these defenses are human-centric, bringing patients into the loop with respect to the security and privacy of their implantable medical devices (IMDs). Our contributions provide a scientific baseline for understanding the potential security and privacy risks of current and future IMDs, and introduce human-perceptible and zero-power mitigation techniques that address those risks. To the best of our knowledge, this paper is the first in our community to use general-purpose software radios to analyze and attack previously unknown radio communications protocols.

/pdf/pacemakers-and-implantable-cardiac-defibrillators-software-vwxx55706g.pdf

Pacemakers and Implantable Cardiac Defibrillators: Software Radio Attacks and Zero-Power Defenses

Electromagnetic interference (EMI) affects circuits by inducing voltages on conductors. Analog sensing of signals on the order of a few millivolts is particularly sensitive to interference. This work (1) measures the susceptibility of analog sensor systems to signal injection attacks by intentional, low-power emission of chosen electromagnetic waveforms, and (2) proposes defense mechanisms to reduce the risks. Our experiments use specially crafted EMI at varying power and distance to measure susceptibility of sensors in implantable medical devices and consumer electronics. Results show that at distances of 1-2m, consumer electronic devices containing microphones are vulnerable to the injection of bogus audio signals. Our measurements show that in free air, intentional EMI under 10 W can inhibit pacing and induce defibrillation shocks at distances up to 1-2m on implantable cardiac electronic devices. However, with the sensing leads and medical devices immersed in a saline bath to better approximate the human body, the same experiment decreases to about 5 cm. Our defenses range from prevention with simple analog shielding to detection with a signal contamination metric based on the root mean square of waveform amplitudes. Our contribution to securing cardiac devices includes a novel defense mechanism that probes for forged pacing pulses inconsistent with the refractory period of cardiac tissue.

Ghost Talk: Mitigating EMI Signal Injection Attacks against Analog Sensors

Implantable medical devices, or IMDs, are increasingly being used to improve patients' medical outcomes. Designers of IMDs already balance safety, reliability, complexity, power consumption, and cost. However, recent research has demonstrated that designers should also consider security and data privacy to protect patients from acts of theft or malice, especially as medical technology becomes increasingly connected to other systems via wireless communications or the Internet. This survey paper summarizes recent work on IMD security. It discusses sound security principles to follow and common security pitfalls to avoid. As trends in power efficiency, sensing, wireless systems and bio-interfaces make possible new and improved IMDs, they also underscore the importance of understanding and addressing security and privacy concerns in an increasingly connected world.

/pdf/design-challenges-for-secure-implantable-medical-devices-3uunzyxruy.pdf

Design challenges for secure implantable medical devices

Medical devices based on embedded systems are ubiquitous in clinical settings. Increasingly, they connect to networks and run off-the-shelf operating systems vulnerable to malware. But strict validation requirements make it prohibitively difficult or costly to use anti-virus software or automated operating system updates on these systems. Our add-on monitoring system, WattsUpDoc, uses a traditionally undesirable side channel of power consumption to enable run-time malware detection. In our experiments, WattsUpDoc detected previously known malware with at least 94% accuracy and previously unknown malware with at least 85% accuracy on several embedded devices--detection rates similar to those of conventional malware-detection systems on PCs. WattsUpDoc detects malware without requiring hardware or software modifications or network communication.

/pdf/wattsupdoc-power-side-channels-to-nonintrusively-discover-q5lwgjcj7g.pdf

WattsUpDoc: power side channels to nonintrusively discover untargeted malware on embedded medical devices

Mobile sensing is difficult without power. Emerging Computational RFIDs (CRFIDs) provide both sensing and general-purpose computation without batteries--instead relying on small capacitors charged by energy harvesting. CRFIDs have small form factors and consume less energy than traditional sensor motes. However, CRFIDs have yet to see widespread use because of limited autonomy and the propensity for frequent power loss as a result of the necessarily small capacitors that serve as a microcontroller's power supply. Our results show that hybrid harvesting CRFIDs, which use an ambient energy micro-harvester, can complete a variety of useful workloads--even in an environment with little ambient energy available.Our contributions include (1) benchmarks demonstrating that micro-harvesting from ambient energy sources enables greater range and read rate, as well as autonomous operation by hybrid CRFIDs, (2) a measurement study that stresses the limits of effective ambient energy harvesting for diverse workloads, (3) application studies that demonstrate the benefits of hybrid CRFIDs, and (4) a trace-driven simulator to model and evaluate the expected behavior of a CRFID with different capacitor sizes and operating under varying conditions of mobility and solar energy harvesting. Our results show that ambient harvesting can triple the effective communication range of a CRFID, quadruple the read rate, and achieve 95% uptime in RAM retention mode despite long periods of low light.

/pdf/on-the-limits-of-effective-hybrid-micro-energy-harvesting-on-1fxnf0u4n7.pdf

Shane S. Clark

Papers

Pacemakers and Implantable Cardiac Defibrillators: Software Radio Attacks and Zero-Power Defenses

Ghost Talk: Mitigating EMI Signal Injection Attacks against Analog Sensors

Design challenges for secure implantable medical devices

WattsUpDoc: power side channels to nonintrusively discover untargeted malware on embedded medical devices

On the limits of effective hybrid micro-energy harvesting on mobile CRFID sensors