| 1. |
- Eriksson, Joakim
(författare)
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Scalable and Interoperable Low-Power Internet of Things Networks
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Internet of Things (IoT) is the concept of connecting devices to the Internet. IoT devices can be anything from small temperature sensors to self-driving cars. The devices are typically resource-constrained, connected wirelessly, and often battery-powered. In this thesis, we address energy efficiency and the tools required for estimating power consumption, interoperability between different implementations of IoT protocols, and scalability of the IoT networks in mesh configurations. The contributions are made in the five included research papers addressing these challenges. Firstly, we present and evaluate network-wide energy estimation support in our simulation tool COOJA/MSPSim. Due to the timing accuracy of the simulation and emulation, we get energy consumption estimates very close to hardware-based estimates. The second contribution evaluates the capabilities of simulation tools for interoperability testing. We show that it is possible to set up simulations of networks with multiple implementations of the same open standards (6LoWPAN/RPL) and that it is possible to get results beyond pure interoperability, including power consumption and network quality. Finally, we show that, by carefully managing neighbor updates, it is possible to scale IoT networks even when the IoT devices' memory limitations severely constrain the size of the neighbor table.The experimental systems research that resulted in this thesis also provided significant contributions to the open-source ecosystem around Contiki, an operating system for resource-constrained IoT devices. This software, Contiki and COOJA/MSPSim, has been a cornerstone in our capability to perform sound systems research and has been widely used by other research groups in resource-constrained IoT research in academia and many companies for developing commercial IoT devices.
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| 2. |
- He, Zhitao
(författare)
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Enabling Scalable Security in Internet of Things
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The popular notion of Internet of Things (IoT) implies two salient features: 1. a diversity of small things, i.e., constrained devices; 2. their seamless integration with the Internet. Pioneering work in Wireless Sensor Networks (WSNs) have laid a solid technological foundation for autonomous, low power wireless communication among battery-powered, microcontroller-based devices. On the other hand, as devices are being connected to the Internet in large numbers, industry experts and regulators have associated IoT with enormous security risk. Sensitive personal information, highly complex business workflows, and critical infrastructure for public safety are at stake. In this dissertation, we first explore the scalability of IoT. Approaching from the particular angle of radio interference, we study unstable and faulty network behavior when links between low power radios are disrupted. Our low cost and practical interference generation tools fill a gap between protocol design and test. We then underline the threat of novel attacks at the physical layer, which lead to denial of service and battery draining of low power radios. Launched from low cost hardware, the attacks we devise are power-efficient and hard to detect; and they reach longer ranges than jamming. Finally, we take a step closer to realization of secure and large-scale IoT deployment by enabling certificate enrollment, a key component in a public key infrastructure, for small devices. We show that automated enrollment of device certificates becomes feasible when a memory and power efficient IoT protocol stack is leveraged. Spanning between the physical layer and the application layer, our work has enriched the knowledge domain of IoT and advanced the technological frontier of scalable and secure IoT deployment.
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| 3. |
- Hewage, Kasun
(författare)
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Towards Secure Synchronous Communication Architectures for Wireless Networks
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The vision behind the Internet of Things (IoT) revolves around creating a connected ecosystem where devices, people, and systems collaborate seamlessly, unlocking new possibilities, improving efficiency, and enhancing our daily lives. IoT encloses many device classes, including low-power wireless devices that rely on batteries or energy harvesting. Due to the low-power nature and the instability of the wireless links, networks comprising these IoT devices are commonly known as Low-power and Lossy Networks (LLNs).Several network-wide flooding-based communication primitives that employ synchronous transmissions have emerged as an alternative to traditional multi-hop routing, thereby creating a new dimension of LLN research. While these primitives have demonstrated superior performance in terms of latency and reliability, they have received little attention regarding network security. In this dissertation, we study the effectiveness of several attacks that strive to disrupt synchronous transmission-based protocols. Based on the findings from this work, we examine the security requirements and propose encryption and lightweight flood verification methods to protect synchronous transmission-based flooding protocols from these attacks.Realising the IoT's vision demands employing well-established communication technologies like the Internet Protocol (IP) suite protocols to ensure interoperability. However, the IP suite protocols are not explicitly designed for low-power networks; hence using them in LLNs encounters numerous challenges. Some of my work included in this dissertation focuses on the performance issues of two widely used IP suite protocols: Transmission Control Protocol (TCP) and Datagram Transport Layer Security (DTLS). We propose to replace the conventional link layer protocols of the LLN stacks with a synchronous transmission-based protocol to enhance the reliability that TCP expects in lower layers, thereby improving the TCP performance. We introduce novel header compression mechanisms to reduce the size of DTLS messages without violating end-to-end security. Reducing the size of DTLS messages lowers the transmission overhead, improving its performance in LLNs.Optical Wireless Communication (OWC) is a complementary technology to radio frequency communication. Specifically, visible light communication (VLC) has proven its capability to offer higher data transfer rates, enabling faster and more efficient communication. The last work of this dissertation draws inspiration from synchronous transmissions in LLNs and presents an OWC-based time synchronisation system for high-speed VLC access points to synchronise their transmissions. This time synchronisation system has a considerably lower synchronisation jitter than the widely-used Precision Time Protocol (PTP).
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| 4. |
- Khurshid, Anum
(författare)
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Towards Trustworthy and Secure Internet of Things Devices : Using hardware-assisted Trusted Execution and Automated Certification
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The advent of Trusted Execution Environments (TEEs) for IoT aligns with the reinforcement of IoT security through recent laws and regulations. A major part of IoT systems comprises of resource-constrained devices, with less margin in memory and computation capabilities to embed sophisticated security solutions. Hence, hardware-based TEEs provide resource-efficient remedies to known attack vectors with reduced software attack surface. In this dissertation, we identified challenges cropping up from the heterogeneity of the IoT infrastructure, that hindered the adoption of TEEs in resource-constrained IoT. We ultimately approach the security of IoT devices through automated certification with hardware-rooted assurance guarantees. The contributions of this dissertation are made through six research papers addressing these challenges. TEEs provide hardware-supported mechanisms to create secure areas to store sensitive data and execute critical software. However, the secure areas lack a secure way to communicate with the rest of the system. Moreover, once a software is placed in the secure areas, it becomes extremely difficult to detect and trace misbehaviour. To this end, we contribute frameworks that strengthen the functionality of TrustZone-M, which is ARM’s TEE designed for resource-constrained IoT. The addition of a secure communication channel in TrustZone-M enabled IoT devices guarantees confidentiality and integrity of shared data between the system applications and the secure areas even in case of a compromised OS. In addition, our contribution to the TrustZone-M secure areas to enable monitoring and blocking of malicious behaviour by applications, adds protection in the presence of untrusted third-party critical software.Secondly, we propose an automated digital certification of IoT devices by combining the Public Key Infrastructure standard authentication mechanisms with attributes of software assurance. The resultant process and the certificate is compliant with standards, bearing potential for seamless integration into existing and forthcoming IoT standards and incorporates assurance guarantees with minimal addition to the existing digital certificate.Lastly, we contribute a software update architecture based on well-vetted standards, proposing token-based access control. The architecture relies on a compact message encoding format to encode the software manifests, providing authorized updates while ensuring small code and message sizes suitable for resource-constrained IoT devices. The experimental evaluations of the proposed solutions in well-defined IoT use-cases, reveal the feasibility of their integration in existing devices with minimal effort. Furthermore, the performance analysis in each case, demonstrates execution overhead at par with system operations. The overall contribution of this dissertation advances the security of resource-constrained heterogeneous IoT devices, with substantial impact in the academic and industrial community. Since TrustZone-M and TPM 2.0 are in the preliminary stages of adoption in the IoT domain, these enhancements and contributions are well-timed for efficient integration, while looking forward to the effective pay-off in the near future.
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| 5. |
- Pérez-Penichet, Carlos
(författare)
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Seamless Integration of Battery-Free Communications in Commodity Wireless Networks
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ubiquitous sensing applications have countless potential benefits to society. However, batteries have long been an obstacle to their full development. Harvesting energy from the environment is a promising alternative to battery power, but traditional radio transceivers consume too much for most harvesters. This work is motivated by backscatter communications, a technique that reduces the energy that devices spend exchanging data by up to three orders of magnitude relative to regular radios. This reduction enables sensing devices that operate indefinitely without having to replace batteries; instead they leverage energy harvesting. My goal is to enable the seamless integration of battery-free devices with widespread low-power commodity networks such as Bluetooth or ZigBee/IEEE 802.15.4. Making this integration seamless is critical for the broad adoption of the new class of devices.At a high level, my dissertation outlines a series of challenges to the seamless integration of the new devices with regular low-power networks. We then propose ways to address these challenges, and demonstrate how we could integrate ultra-low-power battery-free devices with regular networks, while avoiding hardware modifications and minimizing any disruption that the addition may cause to existing and co-located communication devices.This work advances the state of the art by: First, demonstrating how to augment an existing sensor network with new sensors without any hardware modification to the pre-existing hardware. The existing network provides the unmodulated carrier that the battery-free nodes need to communicate. Second, we demonstrate a radio receiver that, if implemented in silicon, can directly receive low-power commodity wireless signals when assisted by an unmodulated carrier, and with a power consumption of a few hundred microwatts. The receiver makes battery-free devices directly compatible with regular networks. We introduce simulation models and a first-of-its-kind tool to simulate battery-free communications that integrate with regular networks. Finally, we demonstrate how to efficiently provide unmodulated carrier support for battery-free devices in the previous scenarios without unnecessarily spending energy and spectrum and without undue disturbance to co-located devices.
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| 6. |
- Piumwardane, Dilushi, 1992-
(författare)
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Multi-Tag Backscatter Networks
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are billions of Internet of Things (IoT) devices distributed across the globe, and this growing number of interconnected IoT devices demand seamless networking and low-power communication. While many devices are powered with batteries, their limitations such as maintenance and environmental impact call for battery-free alternatives. Small battery-free devices are attractive for sensing as they can use backscatter communication and operate on harvested energy from their surroundings. This dissertation presents a collection of novel techniques for backscatter communication, a method that reduces energy consumption by several orders of magnitude compared to standard low-power radio communication. Backscatter communication provides a direction for implementing widespread networks of battery-free devices that can be used for ubiquitous sensing. However, real-world deployment of backscatter tags encounters challenges due to their constrained power budgets. Adding mechanisms for identification, scheduling, querying and relaying for backscatter should be done carefully offloading power consuming components and delegating tasks whenever possible to an external powerful device.This dissertation advances the state of the art in two different kinds of backscatter networks: digital backscatter networks and analog backscatter networks. Like conventional RF devices, protocol-based digital backscatter tags encode and communicate binary data in packets, allowing these tags to interoperate with conventional IoT devices using protocols such as IEEE 802.15.4. Applications such as dense networks require tag-to-tag multi-hop communication which introduces challenges as the tags rely on an external signal. For digital backscatter, I present protocol-based multi-hop communication and develop a tool to test large tag-to-tag networks. By contrast, analog backscatter directly communicates the sensor readings by modulating the external signal. As the analog tags lack a packet structure and onboard computation, these tags require new ways to provide key network functionality. For analog backscatter I propose and implement novel techniques for identification, querying and reading high resolution sensor data without significantly increasing the limited power budget on the tag. The contributions outlined in this dissertation enable practical deployment of backscatter tags for sensing and communication applications.
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| 7. |
- Yan, Wenqing, Ph.D. Student, 1994-
(författare)
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Design and Identification of Wireless Transmitters for a Low-power and Secure Internet of Things
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless communication is a key enabler for connecting billions of Internet of Things devices. For networked embedded devices operating on limited energy resources, wireless communication dominates the power consumption. Moreover, as networked devices increasingly handle sensitive data, security concerns in wireless communication are continuously expanding. This dissertation develops novel solutions for low-power and secure wireless communication. Wireless transmitters consist of a series of steps, involving both analog and digital components, each playing a distinct role in the transmit chain. Conventional transmitters employ power-hungry analog components, leading to power consumption on the order of milliwatt. Backscatter transmitters significantly reduce communication power consumption to levels well below one milliwatt. This remarkable power efficiency is achieved by offloading power-hungry components to an external carrier emitter. However, backscatter transmitters encounter challenges in applications that demand medium to long communication range, because they rely heavily on powerful emitters in their proximity for an effective communication range. Instead of removing power-hungry components, our solution integrates the functions of these components into a low-power design. While still requiring an emitter, our transmitter does not reflect the carrier signal. Instead, we utilize a weak carrier signal to stabilize the transmitter, allowing a communication range of over one hundred meters even when the emitter is far away. This contribution takes a step forward in moving low-power communication beyond backscatter.Passive radiometric fingerprinting leverages imperfections of hardware components to identify and authenticate transmitters. Its passive nature fits well to secure low-power transmitters operating within constrained resources. To enhance the viability of radiometric fingerprinting, we make three contributions in this dissertation to facilitate its widespread deployment. First, compared to conventional radios, low-power backscatter communication has a fundamentally different composition of hardware components in its transmit chain. In our work, we decompose fingerprints in a backscatter system for dual identification of tags and emitters. Beyond security purposes, recognizing the emitter embeds a notion of locality, enabling fingerprinting usage in backscatter network management tasks such as emitter coordination. Second, the dynamic nature of real-world wireless channels significantly impacts the robustness of fingerprinting. We decompose channel impacts and develop a hybrid system. This system employs pertinent strategies for different channel factors, ensuring reliable performance across complex wireless conditions. Lastly, based on the understanding of components' contributions to the transmit chain, we design a lightweight fingerprinting system. We demonstrate a complete implementation seamlessly integrated within the constraints of a single low-cost off-the-shelf chip. This contribution simplifies the conventionally bulky setup using sophisticated signal acquisition equipment and dedicated computer processing resources, which facilitates the practical deployment of fingerprinting on low-cost embedded devices.
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