This thesis aimed to create a messaging protocol for OpenSpace to interoperate with other astronomy software. The goal was to create a messaging standard that was not language-dependent and could be implemented by any astronomy software. To establish an asynchronous communication between OpenSpace and connected software, the Transmission Control Protocol (TCP), threading, and Peer-To-Peer (P2P) were the techniques mainly used. TCP was used to achieve reliable communication between software connected to the network. The enabling of two-way communication was solved by threading. P2P was used as a network communication architecture to share resources between the connected software. By using Unicode characters expressed through UTF-8, the Unicode Standard was used to encode messages sent. The messages are structured by combinations of different sizes of bytes and are sent and received as binary strings. All messages contain a header and the data being sent. Different message types were created to specify which type of data is sent. The protocol works primarily between OpenSpace and Glue but is not limited to these software. The implementation serves as the basis of the messaging protocol for OpenSpace, where Glue represents future software integrations.

Over the last two decades, mobile computing has gone from being a mere vision to becoming a reality, ubiquitously present in our everyday lives. There are different types of mobility, from user and terminal mobility, to mobility of services and sessions. This thesis is mainly about application mobility { the ability for an application to migrate between different host devices during its execution. The aim of this thesis work is to explore and advance the area of application mobility. The thesis approaches this goal through focusing on three research issues: Architectural considerations for application mobility; Context-awareness support and application adaptability; and Concept exploration.The contributions of this thesis include the identification of requirements for application mobility and a proposal for a decentralized, global scale architecture for application mobility, building on the peer-to-peer paradigm. Several prototypes of systems allowing application mobility are deployed, manifesting concepts such as decentralized system layout, context-awareness, context quality and global scope. Evaluations are both quantitative and qualitative. Other contributions of this thesis are the design and evaluation of a framework building on cloud and peer-to-peer technology to enable mobile sessions and an exploration of the concept of application mobility. / Sense Smart City, MOSA - mobil och öppen tjänste-access, NIMO - Nordic Interaction and Mobility Research Platform

The pilot study used in this thesis examined the attitudes and perceptions of a small group of students at the University of North Texas. The participants in this pilot study (n=22) were administered an online music file sharing survey, a Defining Issues Test (DIT), and participated in a small focus group. This thesis also outlined the history and progression of online music piracy in the United States, and addressed four research questions which aimed to determine why individuals choose to engage in the file sharing of copyrighted music online.

Die Erfindung von Bitcoin hat ein großes Interesse an dezentralen Systemen geweckt. Eine häufige Zuschreibung an dezentrale Systeme ist dabei, dass eine Dezentralisierung automatisch zu einer höheren Sicherheit und Widerstandsfähigkeit gegenüber Angriffen führt. Diese Dissertation widmet sich dieser Zuschreibung, indem untersucht wird, ob dezentralisierte Anwendungen tatsächlich so robust sind. Dafür werden exemplarisch drei Systeme untersucht, die häufig als Komponenten in komplexen Blockchain-Anwendungen benutzt werden: Ethereum als Infrastruktur, IPFS zur verteilten Datenspeicherung und schließlich "Stablecoins" als Tokens mit Wertstabilität. Die Sicherheit und Robustheit dieser einzelnen Komponenten bestimmt maßgeblich die Sicherheit des Gesamtsystems in dem sie verwendet werden; darüber hinaus erlaubt der Fokus auf Komponenten Schlussfolgerungen über individuelle Anwendungen hinaus. Für die entsprechende Analyse bedient sich diese Arbeit einer empirisch motivierten, meist Netzwerklayer-basierten Perspektive -- angereichert mit einer ökonomischen im Kontext von Wertstabilen Tokens. Dieses empirische Verständnis ermöglicht es Aussagen über die inhärenten Eigenschaften der studierten Systeme zu treffen. Ein zentrales Ergebnis dieser Arbeit ist die Entdeckung und Demonstration einer "Eclipse-Attack" auf das Ethereum Overlay. Mittels eines solchen Angriffs kann ein Angreifer die Verbreitung von Transaktionen und Blöcken behindern und Netzwerkteilnehmer aus dem Overlay ausschließen. Des weiteren wird das IPFS-Netzwerk umfassend analysiert und kartografiert mithilfe (1) systematischer Crawls der DHT sowie (2) des Mitschneidens von Anfragenachrichten für Daten. Erkenntlich wird hierbei, dass die hybride Overlay-Struktur von IPFS Segen und Fluch zugleich ist, da das Gesamtsystem zwar robust gegen Angriffe ist, gleichzeitig aber eine umfassende Überwachung der Netzwerkteilnehmer ermöglicht wird. Im Rahmen der wertstabilen Kryptowährungen wird ein Klassifikations-Framework vorgestellt und auf aktuelle Entwicklungen im Gebiet der "Stablecoins" angewandt. Mit diesem Framework wird somit (1) der aktuelle Zustand der Stablecoin-Landschaft sortiert und (2) ein Mittel zur Verfügung gestellt, um auch zukünftige Designs einzuordnen und zu verstehen. / The inception of Bitcoin has sparked a large interest in decentralized systems. In particular, popular narratives imply that decentralization automatically leads to a high security and resilience against attacks, even against powerful adversaries. In this thesis, we investigate whether these ascriptions are appropriate and if decentralized applications are as robust as they are made out to be. To this end, we exemplarily analyze three widely-used systems that function as building blocks for blockchain applications: Ethereum as basic infrastructure, IPFS for distributed storage and lastly "stablecoins" as tokens with a stable value. As reoccurring building blocks for decentralized applications these examples significantly determine the security and resilience of the overall application. Furthermore, focusing on these building blocks allows us to look past individual applications and focus on inherent systemic properties. The analysis is driven by a strong empirical, mostly network-layer based perspective; enriched with an economic point of view in the context of monetary stabilization. The resulting practical understanding allows us to delve into the systems' inherent properties. The fundamental results of this thesis include the demonstration of a network-layer Eclipse attack on the Ethereum overlay which can be leveraged to impede the delivery of transaction and blocks with dire consequences for applications built on top of Ethereum. Furthermore, we extensively map the IPFS network through (1) systematic crawling of its DHT, as well as (2) monitoring content requests. We show that while IPFS' hybrid overlay structure renders it quite robust against attacks, this virtue of the overlay is simultaneously a curse, as it allows for extensive monitoring of participating peers and the data they request. Lastly, we exchange the network-layer perspective for a mostly economic one in the context of monetary stabilization. We present a classification framework to (1) map out the stablecoin landscape and (2) provide means to pigeon-hole future system designs. With our work we not only scrutinize ascriptions attributed to decentral technologies; we also reached out to IPFS and Ethereum developers to discuss results and remedy potential attack vectors.