On robust and secure wireless communication system design using software-defined radios

This dissertation is composed of three parts: airborne multi input multi output (MIMO) communications, physical layer authentication, and software radio design for DARPA Spectrum Challenge. A common theme for the three distinct problems is the system perspective that we have adopted throughout this dissertation. Instead of considering isolated issues within these problems, we have provided a holistic design approach to the three problems and have implemented all three systems using the GNU Radio/USRP (Universal Software Radio Peripheral) platform. In the first part, we develop a MIMO communication system for airborne platforms. MIMO communication has long been considered to be suitable only for environment that is rich in scatterers. This, unfortunately is not the case for airborne platforms. However, this lack of scattering can be compensated by the large aperture of the airborne MIMO platform; this is corroborated by our careful analysis using real measurement data. Our analysis of the airborne MIMO channels leads to the development of a variable rate MIMO transceiver architecture. This architecture is numerically shown to improve the bit error rate (BER) over conventional transceiver architectures that are developed for rich scattering environments. A software radio based MIMO system is then implemented to demonstrate experimentally the efficacy of the developed architecture. In the second part, we develop a physical layer authentication scheme as a counter measure to primary user emulation attack (PUEA) in cognitive radio (CR) networks. In this attack, a malicious user emulates the signal characteristics of the primary user (PU) when it is silent which prevents unsuspecting secondary user (SU) from utilizing the network. The developed physical layer authentication is based on embedding cryptographic hash signatures, referred to as authentication tags, within PU\u27s signal constellations. The embedding is performed such that the legacy receivers are not affected. We analyze the scheme using the fast fading Rayleigh channel model and present an optimal scheme to embed signals in PU\u27s constellations which minimizes the tag BER. Experimental results are obtained that corroborate our theoretical claims, thereby establish that reliable authentication can be achieved without sacrificing signal quality at the primary receivers. In the final part, we describe in detail our design of software radios developed as part of the DARPA Spectrum Challenge (DSC), a year long competition that started in January 2013 and concluded in March 2014 with the final tournament held in Arlington, VA at the DARPA headquarter. DSC was comprised of two tournaments, competitive and cooperative. In the competitive mode two radio pairs, each composed of a transmitter and a receiver, are pitted against each other to transmit the most amount of data error-free while operating concurrently in the same frequency band. In the cooperative mode, three radio pairs have to share a frequency band in a cooperative manner wherein the goal is to maximize the throughput of all the three pairs. We describe the design of our software radio system that integrates some key technologies crucial in operating in an environment that does not allow user coordination and spectrum pre-planning, including: spectrum sensing, adaptive transmission both in spectrum utilization and transmission rate, opportunistic jamming, and sliding window feedback. The developed radio is robust in the presence of unknown interference and achieves the desired balance between throughput and reliability in an uncoordinated transmission environment

Security and Privacy in Dynamic Spectrum Access: Challenges and Solutions

abstract: Dynamic spectrum access (DSA) has great potential to address worldwide spectrum shortage by enhancing spectrum efficiency. It allows unlicensed secondary users to access the under-utilized spectrum when the primary users are not transmitting. On the other hand, the open wireless medium subjects DSA systems to various security and privacy issues, which might hinder the practical deployment. This dissertation consists of two parts to discuss the potential challenges and solutions. The first part consists of three chapters, with a focus on secondary-user authentication. Chapter One gives an overview of the challenges and existing solutions in spectrum-misuse detection. Chapter Two presents SpecGuard, the first crowdsourced spectrum-misuse detection framework for DSA systems. In SpecGuard, three novel schemes are proposed for embedding and detecting a spectrum permit at the physical layer. Chapter Three proposes SafeDSA, a novel PHY-based scheme utilizing temporal features for authenticating secondary users. In SafeDSA, the secondary user embeds his spectrum authorization into the cyclic prefix of each physical-layer symbol, which can be detected and authenticated by a verifier. The second part also consists of three chapters, with a focus on crowdsourced spectrum sensing (CSS) with privacy consideration. CSS allows a spectrum sensing provider (SSP) to outsource the spectrum sensing to distributed mobile users. Without strong incentives and location-privacy protection in place, however, mobile users are reluctant to act as crowdsourcing workers for spectrum-sensing tasks. Chapter Four gives an overview of the challenges and existing solutions. Chapter Five presents PriCSS, where the SSP selects participants based on the exponential mechanism such that the participants' sensing cost, associated with their locations, are privacy-preserved. Chapter Six further proposes DPSense, a framework that allows the honest-but-curious SSP to select mobile users for executing spatiotemporal spectrum-sensing tasks without violating the location privacy of mobile users. By collecting perturbed location traces with differential privacy guarantee from participants, the SSP assigns spectrum-sensing tasks to participants with the consideration of both spatial and temporal factors. Through theoretical analysis and simulations, the efficacy and effectiveness of the proposed schemes are validated.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Enable Reliable and Secure Data Transmission in Resource-Constrained Emerging Networks

The increasing deployment of wireless devices has connected humans and objects all around the world, benefiting our daily life and the entire society in many aspects. Achieving those connectivity motivates the emergence of different types of paradigms, such as cellular networks, large-scale Internet of Things (IoT), cognitive networks, etc. Among these networks, enabling reliable and secure data transmission requires various resources including spectrum, energy, and computational capability. However, these resources are usually limited in many scenarios, especially when the number of devices is considerably large, bringing catastrophic consequences to data transmission. For example, given the fact that most of IoT devices have limited computational abilities and inadequate security protocols, data transmission is vulnerable to various attacks such as eavesdropping and replay attacks, for which traditional security approaches are unable to address. On the other hand, in the cellular network, the ever-increasing data traffic has exacerbated the depletion of spectrum along with the energy consumption. As a result, mobile users experience significant congestion and delays when they request data from the cellular service provider, especially in many crowded areas. In this dissertation, we target on reliable and secure data transmission in resource-constrained emerging networks. The first two works investigate new security challenges in the current heterogeneous IoT environment, and then provide certain countermeasures for reliable data communication. To be specific, we identify a new physical-layer attack, the signal emulation attack, in the heterogeneous environment, such as smart home IoT. To defend against the attack, we propose two defense strategies with the help of a commonly found wireless device. In addition, to enable secure data transmission in large-scale IoT network, e.g., the industrial IoT, we apply the amply-and-forward cooperative communication to increase the secrecy capacity by incentivizing relay IoT devices. Besides security concerns in IoT network, we seek data traffic alleviation approaches to achieve reliable and energy-efficient data transmission for a group of users in the cellular network. The concept of mobile participation is introduced to assist data offloading from the base station to users in the group by leveraging the mobility of users and the social features among a group of users. Following with that, we deploy device-to-device data offloading within the group to achieve the energy efficiency at the user side while adapting to their increasing traffic demands. In the end, we consider a perpendicular topic - dynamic spectrum access (DSA) - to alleviate the spectrum scarcity issue in cognitive radio network, where the spectrum resource is limited to users. Specifically, we focus on the security concerns and further propose two physical-layer schemes to prevent spectrum misuse in DSA in both additive white Gaussian noise and fading environments

Mobile Authentication with NFC enabled Smartphones

Smartphones are becoming increasingly more deployed and as such new possibilities for utilizing the smartphones many capabilities for public and private use are arising. This project will investigate the possibility of using smartphones as a platform for authentication and access control, using near field communication (NFC). To achieve the necessary security for authentication and access control purposes, cryptographic concepts such as public keys, challenge-response and digital signatures are used. To focus the investigation a case study is performed based on the authentication and access control needs of an educational institutions student ID. To gain a more practical understanding of the challenges mobile authentication encounters, a prototype has successfully been developed on the basis of the investigation. The case study performed in this project argues that NFC as a standalone technology is not yet mature to support the advanced communication required by this case. However, combining NFC with other communication technologies such as Bluetooth has proven to be effective. As a result, a general evaluation has been performed on several aspects of the prototype, such as cost-effectiveness, usability, performance and security to evaluate the viability of mobile authentication

FRAMEWORK FOR ANONYMIZED COVERT COMMUNICATIONS: A BLOCKCHAIN-BASED PROOF-OF-CONCEPT

In this dissertation, we present an information hiding approach incorporating anonymity that builds on existing classical steganographic models. Current security definitions are not sufficient to analyze the proposed information hiding approach as steganography offers data privacy by hiding the existence of data, a property that is distinct from confidentiality (data existence is known but access is restricted) and authenticity (data existence is known but manipulation is restricted). Combinations of the latter two properties are common in analyses, such as Authenticated Encryption with Associated Data (AEAD), yet there is a lack of research on combinations with steganography. This dissertation also introduces the security definition of Authenticated Stegotext with Associated Data (ASAD), which captures steganographic properties even when there is contextual information provided alongside the hidden data. We develop a hierarchical framework of ASAD variants, corresponding to different channel demands. We present a real-world steganographic embedding scheme, Authenticated SteGotex with Associated tRansaction Data (ASGARD), that leverages a blockchain-based application as a medium for sending hidden data. We analyze ASGARD in our framework and show that it meets Level-4 ASAD security. Finally, we implement ASGARD on the Ethereum platform as a proof-of-concept and analyze some of the ways an adversary might detect our embedding activity by analyzing historical Ethereum data.Lieutenant, United States NavyApproved for public release. Distribution is unlimited

Authentication enhancement in command and control networks: (a study in Vehicular Ad-Hoc Networks)

Intelligent transportation systems contribute to improved traffic safety by facilitating real time communication between vehicles. By using wireless channels for communication, vehicular networks are susceptible to a wide range of attacks, such as impersonation, modification, and replay. In this context, securing data exchange between intercommunicating terminals, e.g., vehicle-to-everything (V2X) communication, constitutes a technological challenge that needs to be addressed. Hence, message authentication is crucial to safeguard vehicular ad-hoc networks (VANETs) from malicious attacks. The current state-of-the-art for authentication in VANETs relies on conventional cryptographic primitives, introducing significant computation and communication overheads. In this challenging scenario, physical (PHY)-layer authentication has gained popularity, which involves leveraging the inherent characteristics of wireless channels and the hardware imperfections to discriminate between wireless devices. However, PHY-layerbased authentication cannot be an alternative to crypto-based methods as the initial legitimacy detection must be conducted using cryptographic methods to extract the communicating terminal secret features. Nevertheless, it can be a promising complementary solution for the reauthentication problem in VANETs, introducing what is known as “cross-layer authentication.” This thesis focuses on designing efficient cross-layer authentication schemes for VANETs, reducing the communication and computation overheads associated with transmitting and verifying a crypto-based signature for each transmission. The following provides an overview of the proposed methodologies employed in various contributions presented in this thesis. 1. The first cross-layer authentication scheme: A four-step process represents this approach: initial crypto-based authentication, shared key extraction, re-authentication via a PHY challenge-response algorithm, and adaptive adjustments based on channel conditions. Simulation results validate its efficacy, especially in low signal-to-noise ratio (SNR) scenarios while proving its resilience against active and passive attacks. 2. The second cross-layer authentication scheme: Leveraging the spatially and temporally correlated wireless channel features, this scheme extracts high entropy shared keys that can be used to create dynamic PHY-layer signatures for authentication. A 3-Dimensional (3D) scattering Doppler emulator is designed to investigate the scheme’s performance at different speeds of a moving vehicle and SNRs. Theoretical and hardware implementation analyses prove the scheme’s capability to support high detection probability for an acceptable false alarm value ≤ 0.1 at SNR ≥ 0 dB and speed ≤ 45 m/s. 3. The third proposal: Reconfigurable intelligent surfaces (RIS) integration for improved authentication: Focusing on enhancing PHY-layer re-authentication, this proposal explores integrating RIS technology to improve SNR directed at designated vehicles. Theoretical analysis and practical implementation of the proposed scheme are conducted using a 1-bit RIS, consisting of 64 × 64 reflective units. Experimental results show a significant improvement in the Pd, increasing from 0.82 to 0.96 at SNR = − 6 dB for multicarrier communications. 4. The fourth proposal: RIS-enhanced vehicular communication security: Tailored for challenging SNR in non-line-of-sight (NLoS) scenarios, this proposal optimises key extraction and defends against denial-of-service (DoS) attacks through selective signal strengthening. Hardware implementation studies prove its effectiveness, showcasing improved key extraction performance and resilience against potential threats. 5. The fifth cross-layer authentication scheme: Integrating PKI-based initial legitimacy detection and blockchain-based reconciliation techniques, this scheme ensures secure data exchange. Rigorous security analyses and performance evaluations using network simulators and computation metrics showcase its effectiveness, ensuring its resistance against common attacks and time efficiency in message verification. 6. The final proposal: Group key distribution: Employing smart contract-based blockchain technology alongside PKI-based authentication, this proposal distributes group session keys securely. Its lightweight symmetric key cryptography-based method maintains privacy in VANETs, validated via Ethereum’s main network (MainNet) and comprehensive computation and communication evaluations. The analysis shows that the proposed methods yield a noteworthy reduction, approximately ranging from 70% to 99%, in both computation and communication overheads, as compared to the conventional approaches. This reduction pertains to the verification and transmission of 1000 messages in total

Security and Privacy for Modern Wireless Communication Systems

The aim of this reprint focuses on the latest protocol research, software/hardware development and implementation, and system architecture design in addressing emerging security and privacy issues for modern wireless communication networks. Relevant topics include, but are not limited to, the following: deep-learning-based security and privacy design; covert communications; information-theoretical foundations for advanced security and privacy techniques; lightweight cryptography for power constrained networks; physical layer key generation; prototypes and testbeds for security and privacy solutions; encryption and decryption algorithm for low-latency constrained networks; security protocols for modern wireless communication networks; network intrusion detection; physical layer design with security consideration; anonymity in data transmission; vulnerabilities in security and privacy in modern wireless communication networks; challenges of security and privacy in node–edge–cloud computation; security and privacy design for low-power wide-area IoT networks; security and privacy design for vehicle networks; security and privacy design for underwater communications networks

Roadmap on optical security

Postprint (author's final draft

Physical Layer Defenses Against Primary User Emulation Attacks

Cognitive Radio (CR) is a promising technology that works by detecting unused parts of the spectrum and automatically reconfiguring the communication system\u27s parameters in order to operate in the available communication channels while minimizing interference. CR enables efficient use of the Radio Frequency (RF) spectrum by generating waveforms that can coexist with existing users in licensed spectrum bands. Spectrum sensing is one of the most important components of CR systems because it provides awareness of its operating environment, as well as detecting the presence of primary (licensed) users of the spectrum