Health privacy : methods for privacy-preserving data sharing of methylation, microbiome and eye tracking data

This thesis studies the privacy risks of biomedical data and develops mechanisms for privacy-preserving data sharing. The contribution of this work is two-fold: First, we demonstrate privacy risks of a variety of biomedical data types such as DNA methylation data, microbiome data and eye tracking data. Despite being less stable than well-studied genome data and more prone to environmental changes, well-known privacy attacks can be adopted and threaten the privacy of data donors. Nevertheless, data sharing is crucial to advance biomedical research given that collection the data of a sufficiently large population is complex and costly. Therefore, we develop as a second step privacy- preserving tools that enable researchers to share such biomedical data. and second, we equip researchers with tools to enable privacy-preserving data sharing. These tools are mostly based on differential privacy, machine learning techniques and adversarial examples and carefully tuned to the concrete use case to maintain data utility while preserving privacy.Diese Dissertation beleuchtet Risiken für die Privatsphäre von biomedizinischen Daten und entwickelt Mechanismen für privatsphäre-erthaltendes Teilen von Daten. Dies zerfällt in zwei Teile: Zunächst zeigen wir die Risiken für die Privatsphäre auf, die von biomedizinischen Daten wie DNA Methylierung, Mikrobiomdaten und bei der Aufnahme von Augenbewegungen vorkommen. Obwohl diese Daten weniger stabil sind als Genomdaten, deren Risiken der Forschung gut bekannt sind, und sich mehr unter Umwelteinflüssen ändern, können bekannte Angriffe angepasst werden und bedrohen die Privatsphäre der Datenspender. Dennoch ist das Teilen von Daten essentiell um biomedizinische Forschung voranzutreiben, denn Daten von einer ausreichend großen Studienpopulation zu sammeln ist aufwändig und teuer. Deshalb entwickeln wir als zweiten Schritt privatsphäre-erhaltende Techniken, die es Wissenschaftlern erlauben, solche biomedizinischen Daten zu teilen. Diese Techniken basieren im Wesentlichen auf differentieller Privatsphäre und feindlichen Beispielen und sind sorgfältig auf den konkreten Einsatzzweck angepasst um den Nutzen der Daten zu erhalten und gleichzeitig die Privatsphäre zu schützen

Privacy-Protecting Techniques for Behavioral Data: A Survey

Our behavior (the way we talk, walk, or think) is unique and can be used as a biometric trait. It also correlates with sensitive attributes like emotions. Hence, techniques to protect individuals privacy against unwanted inferences are required. To consolidate knowledge in this area, we systematically reviewed applicable anonymization techniques. We taxonomize and compare existing solutions regarding privacy goals, conceptual operation, advantages, and limitations. Our analysis shows that some behavioral traits (e.g., voice) have received much attention, while others (e.g., eye-gaze, brainwaves) are mostly neglected. We also find that the evaluation methodology of behavioral anonymization techniques can be further improved

Mobile eye tracking applied as a tool for customer experience research in a crowded train station

Train stations have increasingly become crowded, necessitating stringent requirements in the design of stations and commuter navigation through these stations. In this study, we explored the use of mobile eye tracking in combination with observation and a survey to gain knowledge on customer experience in a crowded train station. We investigated the utilization of mobile eye tracking in ascertaining customers’ perception of the train station environment and analyzed the effect of a signalization prototype (visual pedestrian flow cues), which was intended for regulating pedestrian flow in a crowded underground passage. Gaze behavior, estimated crowd density, and comfort levels (an individual’s comfort level in a certain situation), were measured before and after the implementation of the prototype. The results revealed that the prototype was visible in conditions of low crowd density. However, in conditions of high crowd density, the prototype was less visible, and the path choice was influenced by other commuters. Hence, herd behavior appeared to have a stronger effect than the implemented signalization prototype in conditions of high crowd density. Thus, mobile eye tracking in combination with observation and the survey successfully aided in understanding customers’ perception of the train station environment on a qualitative level and supported the evaluation of the signalization prototype the crowded underground passage. However, the analysis process was laborious, which could be an obstacle for its practical use in gaining customer insights

Towards Everyday Virtual Reality through Eye Tracking

Durch Entwicklungen in den Bereichen Computergrafik, Hardwaretechnologie, Perception Engineering und Mensch-Computer Interaktion, werden Virtual Reality und virtuelle Umgebungen immer mehr in unser tägliches Leben integriert. Head-Mounted Displays werden jedoch im Vergleich zu anderen mobilen Geräten, wie Smartphones und Smartwatches, noch nicht so häufig genutzt. Mit zunehmender Nutzung dieser Technologie und der Gewöhnung von Menschen an virtuelle Anwendungsszenarien ist es wahrscheinlich, dass in naher Zukunft ein alltägliches Virtual-Reality-Paradigma realisiert wird. Im Hinblick auf die Kombination von alltäglicher Virtual Reality und Head-Mounted-Displays, ist Eye Tracking eine neue Technologie, die es ermöglicht, menschliches Verhalten in Echtzeit und nicht-intrusiv zu messen. Bevor diese Technologien in großem Umfang im Alltag eingesetzt werden können, müssen jedoch noch zahlreiche Aspekte genauer erforscht werden. Zunächst sollten Aufmerksamkeits- und Kognitionsmodelle in Alltagsszenarien genau verstanden werden. Des Weiteren sind Maßnahmen zur Wahrung der Privatsphäre notwendig, da die Augen mit visuellen biometrischen Indikatoren assoziiert sind. Zuletzt sollten anstelle von Studien oder Anwendungen, die sich auf eine begrenzte Anzahl menschlicher Teilnehmer mit relativ homogenen Merkmalen stützen, Protokolle und Anwendungsfälle für eine bessere Zugänglichkeit dieser Technologie von wesentlicher Bedeutung sein. In dieser Arbeit wurde unter Berücksichtigung der oben genannten Punkte ein bedeutender wissenschaftlicher Vorstoß mit drei zentralen Forschungsbeiträgen in Richtung alltäglicher Virtual Reality unternommen. Menschliche visuelle Aufmerksamkeit und Kognition innerhalb von Virtual Reality wurden in zwei unterschiedlichen Bereichen, Bildung und Autofahren, erforscht. Die Forschung im Bildungsbereich konzentrierte sich auf die Auswirkungen verschiedener Manipulationen im Klassenraum auf das menschliche Sehverhalten, während die Forschung im Bereich des Autofahrens auf sicherheitsrelevante Fragen und Blickführung abzielte. Die Nutzerstudien in beiden Bereichen zeigen, dass Blickbewegungen signifikante Implikationen für diese alltäglichen Situationen haben. Der zweite wesentliche Beitrag fokussiert sich auf Privatsphäre bewahrendes Eye Tracking für Blickbewegungsdaten von Head-Mounted Displays. Dies beinhaltet Differential Privacy, welche zeitliche Korrelationen von Blickbewegungssignalen berücksichtigt und Privatsphäre wahrende Blickschätzung durch Verwendung eines auf randomisiertem Encoding basierenden Frameworks, welches Augenreferenzunkte verwendet. Die Ergebnisse beider Arbeiten zeigen, dass die Wahrung der Privatsphäre möglich ist und gleichzeitig der Nutzen in einem akzeptablen Bereich bleibt. Wenngleich es bisher nur wenig Forschung zu diesem Aspekt von Eye Tracking gibt, ist weitere Forschung notwendig, um den alltäglichen Gebrauch von Virtual Reality zu ermöglichen. Als letzter signifikanter Beitrag, wurde ein Blockchain- und Smart Contract-basiertes Protokoll zur Eye Tracking Datenerhebung für Virtual Reality vorgeschlagen, um Virtual Reality besser zugänglich zu machen. Die Ergebnisse liefern wertvolle Erkenntnisse für alltägliche Nutzung von Virtual Reality und treiben den aktuellen Stand der Forschung in mehrere Richtungen voran.With developments in computer graphics, hardware technology, perception engineering, and human-computer interaction, virtual reality and virtual environments are becoming more integrated into our daily lives. Head-mounted displays, however, are still not used as frequently as other mobile devices such as smart phones and watches. With increased usage of this technology and the acclimation of humans to virtual application scenarios, it is possible that in the near future an everyday virtual reality paradigm will be realized. When considering the marriage of everyday virtual reality and head-mounted displays, eye tracking is an emerging technology that helps to assess human behaviors in a real time and non-intrusive way. Still, multiple aspects need to be researched before these technologies become widely available in daily life. Firstly, attention and cognition models in everyday scenarios should be thoroughly understood. Secondly, as eyes are related to visual biometrics, privacy preserving methodologies are necessary. Lastly, instead of studies or applications utilizing limited human participants with relatively homogeneous characteristics, protocols and use-cases for making such technology more accessible should be essential. In this work, taking the aforementioned points into account, a significant scientific push towards everyday virtual reality has been completed with three main research contributions. Human visual attention and cognition have been researched in virtual reality in two different domains, including education and driving. Research in the education domain has focused on the effects of different classroom manipulations on human visual behaviors, whereas research in the driving domain has targeted safety related issues and gaze-guidance. The user studies in both domains show that eye movements offer significant implications for these everyday setups. The second substantial contribution focuses on privacy preserving eye tracking for the eye movement data that is gathered from head-mounted displays. This includes differential privacy, taking temporal correlations of eye movement signals into account, and privacy preserving gaze estimation task by utilizing a randomized encoding-based framework that uses eye landmarks. The results of both works have indicated that privacy considerations are possible by keeping utility in a reasonable range. Even though few works have focused on this aspect of eye tracking until now, more research is necessary to support everyday virtual reality. As a final significant contribution, a blockchain- and smart contract-based eye tracking data collection protocol for virtual reality is proposed to make virtual reality more accessible. The findings present valuable insights for everyday virtual reality and advance the state-of-the-art in several directions

Privacy-Preserving Gaze Data Streaming in Immersive Interactive Virtual Reality: Robustness and User Experience

Eye tracking is routinely being incorporated into virtual reality (VR) systems. Prior research has shown that eye tracking data, if exposed, can be used for re-identification attacks. The state of our knowledge about currently existing privacy mechanisms is limited to privacy-utility trade-off curves based on data-centric metrics of utility, such as prediction error, and black-box threat models. We propose that for interactive VR applications, it is essential to consider user-centric notions of utility and a variety of threat models. We develop a methodology to evaluate real-time privacy mechanisms for interactive VR applications that incorporate subjective user experience and task performance metrics. We evaluate selected privacy mechanisms using this methodology and find that re-identification accuracy can be decreased to as low as 14% while maintaining a high usability score and reasonable task performance. Finally, we elucidate three threat scenarios (black-box, black-box with exemplars, and white-box) and assess how well the different privacy mechanisms hold up to these adversarial scenarios. This work advances the state of the art in VR privacy by providing a methodology for end-to-end assessment of the risk of re-identification attacks and potential mitigating solutions.Comment: To appear in IEEE Transactions on Visualization and Computer Graphic

Privacy-Preserving Gaze Data Streaming in Immersive Interactive Virtual Reality:Robustness and User Experience

Eye tracking is routinely being incorporated into virtual reality (VR) systems. Prior research has shown that eye tracking data, if exposed, can be used for re-identification attacks [14]. The state of our knowledge about currently existing privacy mechanisms is limited to privacy-utility trade-off curves based on data-centric metrics of utility, such as prediction error, and black-box threat models. We propose that for interactive VR applications, it is essential to consider user-centric notions of utility and a variety of threat models. We develop a methodology to evaluate real-time privacy mechanisms for interactive VR applications that incorporate subjective user experience and task performance metrics. We evaluate selected privacy mechanisms using this methodology and find that re-identification accuracy can be decreased to as low as 14% while maintaining a high usability score and reasonable task performance. Finally, we elucidate three threat scenarios (black-box, black-box with exemplars, and white-box) and assess how well the different privacy mechanisms hold up to these adversarial scenarios. This work advances the state of the art in VR privacy by providing a methodology for end-to-end assessment of the risk of re-identification attacks and potential mitigating solutions

The Role of Eye Gaze in Security and Privacy Applications: Survey and Future HCI Research Directions

For the past 20 years, researchers have investigated the use of eye tracking in security applications. We present a holistic view on gaze-based security applications. In particular, we canvassed the literature and classify the utility of gaze in security applications into a) authentication, b) privacy protection, and c) gaze monitoring during security critical tasks. This allows us to chart several research directions, most importantly 1) conducting field studies of implicit and explicit gaze-based authentication due to recent advances in eye tracking, 2) research on gaze-based privacy protection and gaze monitoring in security critical tasks which are under-investigated yet very promising areas, and 3) understanding the privacy implications of pervasive eye tracking. We discuss the most promising opportunities and most pressing challenges of eye tracking for security that will shape research in gaze-based security applications for the next decade