Mobile ad hoc networks (MANETs), due to their unique characteristics (e.g., unsecured wireless channel, dynamic mobility, absence of central supportive infrastructure and limited resources), are suffering from a wide range of security threats and attacks. Particularly, MANETs are susceptible to the Denial of Service (DoS) attack that aims to disrupt the network by consuming its resources. In MANETs, a special form of DoS attack has emerged recently as a potentially major threat: the flooding attack. This attack recruits multiple attack nodes to flood the MANET with overwhelming broadcast traffic. This flooding traffic is so large that all, or most of, MANET resources are exhausted. As a result, the MANET is not able to provide any services. This thesis aims to investigate the flooding attack and propose detective security measures to defend MANETs against such an attack.

<div> <div> <div> <p>Billions of “smart” things in our lives have been equipped with various sensors. Current devices, such as smartphones, smartwatches, tablets, and VR/AR headsets, are equipped with a variety of embedded sensors, e.g. accelerometer, gyroscope, magnetometer, camera, GPS sensor, etc. Based on these sensor data, many technologies have been developed to track human motion at different granularities and to enable new applications. This dissertation examines two challenging problems in human motion tracking. One problem is the ID association issue when utilizing external sensors to simultaneously track multiple people. Although an “outside” system can track all human movements in a designated area, it needs to digitally associate each tracking trajectory to the corresponding person, or say the smart device carried by that person, to provide customized service based on the tracking results. Another problem is the inaccuracy caused by limited sensing information when merely using the embedded sensors located on the devices being tracked. Since sensor data may contain inevitable noises and there is no external beacon used as a reference point for calibration, it is hard to accurately track human motion only with internal sensors.</p><p>In this dissertation, we focus on applying multimodal sensing to perform human motion tracking in mobile systems. To address the two above problems separately, we conduct the following research works. (1) The first work seeks to enable public cameras to send personalized messages to people without knowing their phone addresses. We build a system which utilizes the users’ motion patterns captured by the cameras as their communication addresses, and depends on their smartphones to locally compare the sensor data with the addresses and to accept the correct messages. To protect user privacy, the system requires no data from the users and transforms the motion patterns into low-dimensional codes to prevent motion leaks. (2) To enhance distinguishability and scalability of the camera-to-human communication system, we introduce context features which include both motion patterns and ambience features (e.g. magnetic field, Wi-Fi fingerprint, etc.) to identify people. The enhanced system achieves higher association accuracy and is demonstrated to work with dense people in a retailer, with a fixed-length packet overhead. The first two works explore the potential of widely deployed surveillance cameras and provide a generic underlay to various practical applications, such as automatic audio guide, indoor localization, and sending safety alerts. (3) We close this dissertation with a fine-grained motion tracking system which aims to track the positions of two hand-held motion controllers in a mobile VR system. To achieve high tracking accuracy without external sensors, we introduce new types of information, e.g. ultrasonic ranging among the headset and the controllers, and a kinematic arm model. Effectively fusing this additional information with inertial sensing generates accurate controller positions in real time. Compared with commodity mobile VR controllers which only support rotational tracking, our system provides an interactive VR experience by letting the user actually move the controllers’ positions in a VR scene. To summarize, this dissertation shows that multimodal sensing can further explore the potential power in sensor data and can take sensor-based applications to the next generation of innovation.</p><div><br></div></div></div></div><div><div><div> </div> </div> </div>

<div>This thesis firstly surveys and summarizes the state-of-the-art studies from two research areas in Software Defined Networking (SDN) architecture: (i) control plane scalability and (ii) Quality of Service (QoS)-related problems. It also outlines the potential challenges and open problems that need to be addressed further for more scalable SDN control planes and better and complete QoS abilities in SDN networks. The thesis secondly presents a hierarchical SDN design along with an inter-AS QoS-guaranteed routing approach. This design addresses the scalability problems of control plane and privacy concerns of inter-AS QoS routing philosophies in SDN. After exploring the roots of control plane scalability problems in SDN, the thesis then proposes a metric to quantitatively evaluate the control plane scalability in SDN. Later, the thesis presents a general framework for economic analysis of network architectures and designs. To this end, the thesis defines and utilizes two metrics, Unit Service Cost Scalability and Cost-to-Service, to evaluate how SDN architecture performs compared to MPLS architecture in terms of unit cost for a service and cost of introducing a new service along with giving mathematical models to calculate Capital Expenditures (CAPEX) and Operational Expenditures (OPEX) of a network. Moreover, the thesis studies the problem of optimal final pricing for services by proposing an optimal pricing scheme for a service request with QoS in SDN environment while aiming to maximize benefits of both service providers and customers. Finally, the thesis investigates how programmable network architectures, i.e. SDN, affect the network economics compared to traditional network architectures, i.e. MPLS, in case of failures along with exploring the economic impact of failures in different SDN control plane models. </div>

Η υποστήριξη μικρών ομάδων, (που απαρτίζονται από 2-6 μέλη), οι οποίες συνεργάζονται για την επίτευξη κοινών στόχων, αποτελεί αντικείμενο έρευνας τόσο ανθρωπιστικών όσο και τεχνολογικών επιστημονικών πεδίων. Σήμερα, η τεχνολογία διαδραματίζει σημαντικό ρόλο στη συνεργασία ομάδων με διάφορους τρόπους: ως μέσο που επιτρέπει τo διάλογο από απόσταση ή εκ του σύνεγγυς, το διαμοιρασμό πόρων, τη συντήρηση και καθοδήγηση των μελών της ομάδας, το συντονισμό τους κλπ. Επιπλέον, μπορεί να υποστηρίξει σε μεγάλο βαθμό τον ερευνητή στην ανάλυση των δεδομένων που προκύπτουν από δραστηριότητες αυτού του τύπου με κατάλληλες μεθόδους και εργαλεία. O όρος groupware ή collaborative software (Ellis, Gibbs, Rein, 1991), ο οποίος αποδίδεται στη διατριβή αυτή ως συνεργατικό λογισμικό, περιλαμβάνει υπολογιστικά συστήματα τα οποία προορίζονται για την υποστήριξη ομάδων ανθρώπων διαφορετικών μεγεθών, οι οποίες εμπλέκονται σε δραστηριότητες με κοινούς στόχους. Συστήματα αυτού του τύπου μπορεί να είναι είτε γενικού σκοπού, όπως ηλεκτρονικό ταχυδρομείο, chat, συστήματα τηλεδιάσκεψης, φόρουμ συζητήσεων, wiki κλπ., είτε ειδικά λογισμικά που έχουν κατασκευαστεί για να υποστηρίζουν τη συνεργασία και κάποιες συνεργατικές δραστηριότητες στο χώρο εργασίας ή μάθησης. Προβλήματα που σχετίζονται με τη σχεδίαση συνεργατικού λογισμικού αφορούν αφενός την καλύτερη υποστήριξη των συνεργατικών δραστηριοτήτων, την κατανόηση της τυπικής συμπεριφοράς των μελών των ομάδων και της υποστήριξης που η τρέχουσα τεχνολογία είναι σε θέση να τους προσφέρει. Για το σκοπό αυτό είναι σημαντικό να γίνουν κατανοητοί οι παράγοντες που επηρεάζουν τη συμπεριφορά των ομάδων με αυτά τα χαρακτηριστικά. Η Ψυχολογία (και ειδικότερα η Γνωστική Ψυχολογία) και η Κοινωνιολογία είναι δύο επιστημονικοί κλάδοι που ασχολούνται με την μελέτη της συμπεριφοράς ατόμων που συνεργάζονται σε μικρές ομάδες. Οι επιστήμες αυτές προτείνουν μοντέλα τα οποία περιγράφουν χαρακτηριστικά των συμπεριφορών αυτών. Από αυτές τις επιστημονικές περιοχές αναδεικνύονται στα επόμενα κεφάλαια ορισμένοι από τους παράγοντες που επηρεάζουν τη συμπεριφορά των ατόμων κατά τη συνεργασία ούτως ώστε να διατυπωθεί τελικά πρόταση για το ρόλο της τεχνολογίας στον έλεγχο των παραγόντων αυτών. Η παρούσα διατριβή ασχολείται με το θέμα αφενός της ανάλυσης της συμπεριφοράς και αφετέρου της υποστήριξης με κατάλληλο συνεργατικό λογισμικό μικρών ομάδων που εμπλέκονται σε συνεργατικές δραστηριότητες με στόχο τη μάθηση. Στα πλαίσια αυτά έχουν τεθεί επί μέρους στόχοι, οι οποίοι επιτρέπουν την εμβάθυνση στην περιοχή αυτή: Πρώτος στόχος αποτελεί η ανάλυση ορισμένων κοινωνικών και τεχνολογικών παραμέτρων που επηρεάζουν τη συνεργασία μικρών ομάδων, εν συνεχεία η σχεδίαση και ανάπτυξη ενός πρωτότυπου συνεργατικού λογισμικού το οποίο επιτρέπει τη ρύθμιση των παραμέτρων αυτών, ούτως ώστε να είναι δυνατή η σχεδίαση συνεργατικών δραστηριοτήτων με διαφορετικά χαρακτηριστικά και να είναι δυνατός ο έλεγχος ισχύος των σχετικών θεωρητικών υποθέσεων που αφορούν στην επίδραση τους στη συνεργασία. Για την εξακρίβωση των υποθέσεων αυτών, επιδιώκεται η υποστήριξη της ανάλυσης της συνεργατικής δραστηριότητας της ομάδας όπως καταγράφεται από το ίδιο το συνεργατικό λογισμικό με κατάλληλα εργαλεία και μεθόδους ανάλυσης. Με σχετικές εμπειρικές μελέτες γίνεται έλεγχος της αποτελεσματικότητας των συστημάτων που έχουν αναπτυχθεί είτε ως προς την δυνατότητα υποστήριξης της συνεργατικής συμπεριφοράς, είτε ως προς τη δυνατότητα ανάλυσης της συμπεριφοράς αυτής. Η μεθοδολογία που ακολουθήθηκε για την επίτευξη των στόχων αυτών είναι η εξής. 1. Σχεδιάστηκε και υλοποιήθηκε αρχικά μία πλατφόρμα η οποία επιτρέπει την ανάπτυξη συνεργατικών εφαρμογών με παραμετρικά χαρακτηριστικά. Ο όρος «παραμετρικός» αναφέρεται στο γεγονός ότι στις εφαρμογές αυτές ορισμένοι όροι της συνεργασίας μπορεί κάθε φορά να μεταβάλλονται ώστε να υποστηρίζουν προσδοκώμενη συμπεριφορά των μελών της ομάδας. 2. Κατόπιν δημιουργήθηκε ένα μοντέλο καταγραφής της συνεργατικής δραστηριότητας και μια μεθοδολογία ανάλυσης αυτής. Η μοντελοποίηση αυτή βοηθάει, εκτός των άλλων, στην δημιουργία μετρικών για την υποστήριξη του αναλυτή της συνεργασίας. Τελικά, αναπτύχθηκαν συγκεκριμένα εργαλεία που υποστηρίζουν την μοντελοποίηση αυτή και τα οποία δημιουργούν οπτικοποιήσεις της συνεργατικής δραστηριότητας. 3. Τέλος, με τη βοήθεια δύο διαφορετικών παραμετρικών εφαρμογών (του συνεργατικού λογισμικού ModellingSpace και Synergo) και της μεθοδολογίας ανάλυσης των δεδομένων που προέκυψαν από τη χρήση των εφαρμογών αυτών, διατυπώθηκαν υποθέσεις σε σχέση με συγκεκριμένες παραμέτρους και τον τρόπο που επηρεάζουν τη συνεργασία και διεξήχθησαν εμπειρικές μελέτες για την επιβεβαίωση των υποθέσεων αυτών. Τα συμπεράσματα που προέκυψαν από τις μελέτες αυτές απέδειξαν αφενός ότι η παραμετρική πλατφόρμα που σχεδιάστηκε είναι πράγματι ικανή να βοηθήσει στη δημιουργία ποικίλων συνεργατικών εφαρμογών με παραμετρικούς όρους συνεργασίας και αφετέρου ότι η μεθοδολογία ανάλυσης των συνεργατικών δεδομένων μπορεί πράγματι να βοηθήσει την ανάλυση δεδομένων από συνεργατικές δραστηριότητες και να υποστηρίξει την περαιτέρω κατανόηση των σύνθετων φαινομένων που παρατηρούνται κατά τη συνεργασία μικρών ομάδων με στόχο τη μάθηση. / -

The growth of interactive multimedia (IMM) applications is one of the major driving forces behind the swift evolution of next-generation wireless networks where the traffic is expected to be varying and widely diversified. The amalgamation of multimedia applications on high-speed wireless networks is somewhat a natural evolution. Wireless local area network (WLAN) was initially developed to carry non-real time data. Since this type of traffic is bursty in nature, the channel access schemes were based on contention. However real time traffic (e.g. voice, video and other IMM applications) are different from this traditional data traffic as they have stringent constraints on quality of service (QoS) metrics like delay, jitter and throughput. Employing contention free channel access schemes that are implemented on the point coordination function (PCF), as opposed to the numerous works on the contending access schemes, is the plausible and intuitive approach to accommodate these innate requirements. Published researches show that works have been done on improving the distributed coordination function (DCF) to handle IMM traffic. Since the WLAN traffic today is a mix of both, it is only natural to utilize both, DCF and PCF, in a balanced manner to leverage the inherent strengths of each of them. We saw a scope in this technique and develop a scheme that combines both contention and non-contention based phases to handle heterogeneous traffic in WLAN. Standard access scheme, like 802.11e, improves DCF functionality by trying to emulate the functions of PCF. Researchers have made a multitude of improvements on 802.11e to reduce the costs of implementing the scheme on WLAN. We explore improving the PCF, instead, as this is more stable and implementations would be less costly. The initial part of this research investigates the effectiveness of the point coordination function (PCF) for carrying interactive multimedia traffic in WLAN. The performance statistics of IMM traffic were gathered and analyzed. Our results showed that PCF-based setup for IMM traffic is most suitable for high load scenarios. We confirmed that there is a scope in improving IMM transmissions on WLAN by using the PCF. This is supported by published researches on PCF related schemes in carrying IMM traffic on WLAN. Further investigations, via simulations, revealed that partitioning the superframe (SF) duration according to the need of the IMM traffic has considerable impact on the QoS of the WLAN. A theoretical model has been developed to model the two phases, i.e., PCF and DCF, of WLAN medium access control (MAC). With this model an optimum value of the contention free period (CFP) was calculated to meet the QoS requirement of IMM traffic being transmitted. Treating IMM traffic as data traffic or equating both IMM and non-IMM together could compromise a fair treatment that should be given to these QoS sensitive traffic. A self-adaptive scheme, called MAC with Dynamic Superframe Selection (MDSS) scheme, generates an optimum SF configuration according to the QoS requirements of traversing IMM traffic. That particular scheme is shown to provide a more efficient transmission on WLAN. MDSS maximizes the utilization of CFP while providing fairness to contention period (CP). The performance of MDSS is compared to that of 802.11e, which is taken as the benchmark for comparison. Jitter and delay result for MDSS is relatively lower while throughput is higher. This confirms that MDSS is capable of making significant improvement to the standard access scheme.

<p>The accessibility and flexibility of mobile devices make them an advantageous platform for gaming, but there are hardware limitations that impede the rendering of high-quality graphics. Rendering complex graphics on a mobile device typically results in a delayed image, also known as latency, and is a great discomfort for users of any real-time rendering experience. This study tests the image stream optimization View Bypass within a cloud gaming architecture, surpassing this imposing limitation by processing the high-quality game render on a remote computational server. A two sample for means test is performed to determine significance between two treatments: the control group without the View Bypass algorithm and the experimental group rendering with the View Bypass algorithm. A SSIM index score is calculated comparing the disparity between the remote server image output and the final mobile device image output after optimizations have been performed. This score indicates the overall image structural integrity difference between the two treatments and determines the quality and effectiveness of the tested algorithm.</p>

Cognitive Radio technologies have been touted to be instrumental in solving resource-allocation problems in resource-constrained radio environments. The adaptive computational intelligence of these radios facilitates the dynamic allocation of network resources--particularly, the spectrum, a scarce physical asset. In addition to consumer-driven innovation that is governing the wireless communication ecosystem, its associated infrastructure is being increasingly viewed by governments around the world as critical national security interests--the US Military instituted the DARPA Spectrum Collaboration Challenge which requires competitors to design intelligent radios that leverage optimization, A.I., and game-theoretic strategies in order to efficiently access the RF spectrum in an environment wherein every other competitor is vying for the same limited resources. In this work, we detail the design of our radio, i.e., the design choices made in each layer of the network protocol stack, strategies rigorously derived from convex optimization, the collaboration API, and heuristics tailor-made to tackle the unique scenarios emulated in this DARPA Grand Challenge. We present performance evaluations of key components of our radio in a variety of military and disaster-relief deployment scenarios that mimic similar real-world situations. Furthermore, specifically focusing on channel access in the MAC, we formulate the spectrum sensing and access problem as a POMDP; derive an optimal policy using approximate value iteration methods; prove that our strategy outperforms the state-of-the-art, and facilitates means to control the trade-off between secondary network throughput and incumbent interference; and evaluate this policy on an ad-hoc distributed wireless platform constituting ESP32 radios, in order to study its implementation feasibility.

Counter Unmanned Aerial System (CUAS) security systems have unrealistic performance expectations hyped on marketing and idealistic testing environments. By developing an agent-based model to simulate these systems, an average performance metric can be obtained, thereby providing better representative values of true system performance.<br><br>Due to high cost, excessive risk, and exponentially large parameter possibilities, it is unrealistic to test a CUAS system for optimal performance in the real world. Agent-based simulation can provide the necessary variability at a low cost point and allow for numerous parametric possibilities to provide actionable output from the CUAS system. <br><br>This study describes and documents the Simulation of CUAS Networks and Sensors (SCANS) Framework in a novel attempt at developing a flexible modeling framework for CUAS systems based on device parameters. The core of the framework rests on sensor and communication device agents. These sensors, including Acoustic, Radar, Passive Radio Frequency (RF), and Camera, use input parameters, sensor specifications, and UAS specifications to calculate such values as the sound pressure level, received signal strength, and maximum viewable distance. The communication devices employ a nearest-neighbor routing protocol to pass messages from the system which are then logged by a command and control agent. <br><br>This framework allows for the flexibility of modeling nearly any CUAS system and is designed to be easily adjusted. The framework is capable of reporting true positives, true negatives, and false negatives in terms of UAS detection. For testing purposes, the SCANS Framework was deployed in AnyLogic and models were developed based on existing, published, empirical studies of sensors and detection UAS.<br>

The Internet of Things is deploying large numbers of bare-metal systems that have no protection against memory corruption and control-flow hijacking attacks. These attacks have enabled unauthorized entry to hotel rooms, malicious control of unmanned aerial vehicles, and invasions of privacy. Using static and dynamic analysis these systems can utilize state-of-the-art testing techniques to identify and<br>prevent memory-corruption errors and employ defenses against memory corruption and control-flow hijacking attacks in bare-metal systems that match or exceed those currently employed on desktop systems. This is shown using three case studies.<br><br>(1) EPOXY which, automatically applies data execution prevention, diversity, stack defenses, and separating privileged code from unprivileged code using a novel<br>technique called privileged overlaying. These protections prevent code injection attacks, and reduce the number of privileged instruction to 0.06% verses an unprotected<br>application.<br><br>(2) Automatic Compartments for Embedded Systems (ACES), which automatically creates compartments that enforce data integrity and code isolation within bare-metal applications. ACES enables exploring policies to best meet security and performance requirements for individual applications. Results show ACES' can form 10s of compartments within a single thread and has a 15% runtime overhead on average.<br><br><div>(3) HALucinator breaks the requirement for specialized hardware to perform bare-metal system testing. This enables state-of-the-art testing techniques –e.g., coverage based fuzzing – to scale with the availability of commodity computers, leading to the discovery of exploitable vulnerabilities in bare-metal systems. <br></div><div><br></div><div>Combined, these case studies advance the security of embedded system several decades and provide essential protections for today’s connected devices.</div>

This thesis investigates a method for tackling the verification of parametric systems, systems whose behaviour may depend on the value of one or more parameters. The range of allowable values for such parameters may, in general, be large or unknown. This results in a large number of instances of a system that require verification, one instance for each allowable combination of parameter values. When one or more parameters are unbounded, the family of systems that require verification becomes infinite. Computer protocols are one example of such parametric systems. They may have parameters such as the maximum sequence number or the maximum number of retransmissions. Traditional protocol verification approaches usually only analyse and verify properties of a parametric system for a small range of parameter values. It is impossible to verify in this way every concrete instance of an infinite family of systems. Also, the number of reachable states tends to increase dramatically with increasing parameter values, and thus the well known state explosion phenomenon also limits the range of parameters for which the system can be analysed. In this thesis, we concentrate on the parametric verification of the Stop-and-Wait Protocol (SWP), an elementary flow control protocol. We have used Coloured Petri Nets (CPNs) to model the SWP, operating over an in-order but lossy medium, with two unbounded parameters: the maximum sequence number; and the maximum number of retransmissions. A novel method has been used for symbolically representing the parametric reachability graph of our parametric SWP CPN model. This parametric reachability graph captures exactly the infinite family of reachability graphs resulting from the infinite family of SWP CPNs. The parametric reachability graph is represented symbolically as a set of closed-form algebraic expressions for the nodes and arcs of the reachability graph, expressed in terms of the two parameters. By analysing the reachability graphs of the SWP CPN model for small parameter values, structural regularities in the reachability graphs were identified and exploited to develop the appropriate algebraic expressions for the parametric reachability graph. These expressions can be analysed and manipulated directly, thus the properties that are verified from these expressions are verified for all instances of the system. Several properties of the SWP that are able to be verified directly from the parametric reachability graph have been identified. These include a proof of the size of the parametric reachability graph in terms of both parameters, absence of deadlocks (undesired terminal states), absence of livelocks (undesirable cycles of behaviour from which the protocol cannot escape), absence of dead transitions (actions that can never occur) and the upper bounds on the content of the underlying communication channel. These are verified from the algebraic expressions and thus hold for all parameter values. Significantly, language analysis is also carried out on the parametric SWP. The parametric reachability graph is translated into a parametric Finite State Automaton (FSA), capturing symbolically the infinite set of protocol languages (i.e. sequences of user observable events) by means of similar algebraic expressions to those of the parametric reachability graph. Standard FSA reduction techniques were applied in a symbolic fashion directly to the parametric FSA, firstly to obtain a deterministic representation of the parametric FSA, then to obtain an equivalent minimised FSA. It was found that the determinisation procedure removed the effect of the maximum number of retransmissions parameter, and the minimisation procedure removed the effect of the maximum sequence number parameter. Conformance of all instances of the SWP over both parameters to its desired service language is proved. The development of algebraic expressions to represent the infinite class of Stop-and-Wait Protocols, and the verification of properties (including language analysis) directly from these algebraic expressions, has demonstrated the potential of this method for the verification of more general parametric systems. This thesis provides a significant contribution toward the development of a general parametric verification methodology.