Cieľom tejto práce je navrhnúť platformu na spracovanie a preskúmavanie blockchainu vybraných kryptomien pri použití IPFS. Na riešenie tohoto problému bolo potrobné navrhnúť vlastný decentralizovaný a distribuovaný databázový systém, ktorý podporuje pokročilé dotazy. Vytvorené riešenie poskytuje prehľadné grafické užívateľské rozhranie, ktoré slúži na vizualizáciu dát a taktiež API, vďaka ktorému sa dá systém jednoducho napojiť na iné aplikácie. Prínosom tejto práce je nový pohľad na zpracovávanie blockchainu čo otvára nové možnosti v~jeho prehľadávaní.

abstract: Blockchain technology enables a distributed and decentralized environment without any central authority. Healthcare is one industry in which blockchain is expected to have significant impacts. In recent years, the Healthcare Information Exchange(HIE) has been shown to benefit the healthcare industry remarkably. It has been shown that blockchain could help to improve multiple aspects of the HIE system. When Blockchain technology meets HIE, there are only a few proposed systems and they all suffer from the following two problems. First, the existing systems are not patient-centric in terms of data governance. Patients do not own their data and have no direct control over it. Second, there is no defined protocol among different systems on how to share sensitive data. To address the issues mentioned above, this paper proposes MedFabric4Me, a blockchain-based platform for HIE. MedFabric4Me is a patient-centric system where patients own their healthcare data and share on a need-to-know basis. First, analyzed the requirements for a patient-centric system which ensures tamper-proof sharing of data among participants. Based on the analysis, a Merkle root based mechanism is created to ensure that data has not tampered. Second, a distributed Proxy re-encryption system is used for secure encryption of data during storage and sharing of records. Third, combining off-chain storage and on-chain access management for both authenticability and privacy. MedFabric4Me is a two-pronged solution platform, composed of on-chain and off-chain components. The on-chain solution is implemented on the secure network of Hyperledger Fabric(HLF) while the off-chain solution uses Interplanetary File System(IPFS) to store data securely. Ethereum based Nucypher, a proxy re-encryption network provides cryptographic access controls to actors for encrypted data sharing. To demonstrate the practicality and scalability, a prototype solution of MedFabric4Me is implemented and evaluated the performance measure of the system against an already implemented HIE. Results show that decentralization technology like blockchain could help to mitigate some issues that HIE faces today, like transparency for patients, slow emergency response, and better access control. Finally, this research concluded with the benefits and shortcomings of MedFabric4Me with some directions and work that could benefit MedFabric4Me in terms of operation and performance. / Dissertation/Thesis / Masters Thesis Computer Engineering 2020

On January 15, 2021, the Federal Aviation Administration published the Unmanned Aircraft System Remote Identification rule with the intention of improving airspace security regarding the use of Unmanned Aircraft. According to the rule, UAs in flight must provide the public with information such as their identification, location, and altitude. After the publication of this rule, the IETF DRIP Working Group has been working on the creation of DRIP, a protocol that meets the requirements stipulated in the rule and that guarantees that all the communication involved in the protocol is made trustworthy.  This document presents a thesis project in which Hyperledger Fabric has been studied and evaluated as an alternative to replace DRIP's DNS-based registry management. A vast research procedure combined with experiments has aided in creating a novel Blockchain-based Drone ID architecture called HL-DRIP. The designed system proposes not only how blockchain could be integrated into DRIP, but also how the rest of the Remote ID protocol could be designed, and how each of the protocol's components and participants should interact with each other to make the protocol compliant with the rule. HL-DRIP is a blockchain-based system designed to replace DRIP registry management leveraging Hyperledger Fabric and IPFS. HL-DRIP leverages x.509 and DRIP-based certificates to manage participant registration and authentication. A private IPFS network is deployed by the system's smart contract to manage participants' personal data and mitigate well-known blockchain storage issues, allowing the system to be GDPR-compliant. HL-DRIP supports i) participant registration by using certificates and HIP-based unique IDs, ii) lookups of participants' personal data, and iii) permission management.  HL-DRIP's main functionality has been prototyped and tested. The results have shown that an average of 783 participants are registered with a throughput of 8.1 transactions per second. Furthermore, an average of 648 IPFS data requests are executed with a throughput of 12.8 transactions per second.

Publisering av webbplatser sker traditionellt i ett centraliserat nätverk där en webbserver distribuerar webbplatsens filer till sina klienter. Detta gör det möjligt för större företag eller regeringar att välja vilket innehåll som ska visas och tar bort den frihet som World Wide Web ursprungligen medförde. Att använda ett decentraliserat nätverk som värd för webbplatser kan dock vara fördelaktigt i vissa situationer på grund av de decentraliserade nätverkens höga skalbarhet och skydd mot censur. Denna studie syftar till att fastställa hur en webbplats kan publiceras i ett decentraliserat nätverk och om det kan vara att föredra för vissa typer av webbplatser. Studien syftar också till att ta reda på om det finns några säkerhetsbrister i de decentraliserade nätverken. Detta gjordes genom en litteraturstudie och genom att skapa ett test-system som kan stresstesta en webbplats som ligger på en vanlig webbserver och de decentraliserade lösningarna IPFS och Hypercore. Studien har visat att decentraliserade nätverk i allmänhet distribuerar en webbplats till många klienter snabbare i de flesta situationer. Vidare visas också att det finns några problem för en decentraliserad webbplats som inte finns i en webbplats som ligger på en vanlig webbserver. Bland dessa problem finns det vissa etiska diskussioner att ta hänsyn till när det gäller behandling av personuppgifter, oönskad spridning av olagligt innehåll och möjligheten att radera publicerat innehåll. I studien drogs slutsatsen att om en viss webbplats och dess ägare kan överblicka nackdelarna med ett decentraliserat nätverk bör det med största sannolikhet föredras framför en traditionell webbserver. / Hosting websites is traditionally done in a centralized network where a web server distributes the website’s files to it’s clients. This enables larger companies or governments to choose what content is shown and remove the freedom that the world wide web initially brought. However, using a decentralized network to host websites might be favorable in some situations due to the decentralized networks’ high scalability and protection against censorship. This study aims to determine how a website can be published in a decentralized network and if it can be preferred for some types of websites. The study also aims to find out if there exist any security vulnerabilities in the decentralized networks. This was done by a literature study and by creating a benchmarking system that can stress-test a website hosted on a traditional web server and the decentralized solutions IPFS and Hypercore. The study has shown that decentralized networks generally distribute a website to many clients faster in most situations. Further, it is also shown that there exists a few problems for a decentralized website that is not present in a website hosted on a traditional web server. Among these problems, there are some ethical discussions to be considered regarding the processing of personal data, unwanted distribution of illegal content, and the possibility of deleting published content. The study concluded that if a given website and its owner can oversee the disadvantages of a decentralized network, it should most likely be preferred over a traditional web server

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.

This thesis studies the characteristics of data hosted on the interplanetary name system, which is a part of the interplanetary file system. From these records, information such as file names, locations, and sizes, was investigated. Data was collected on the number of peers hosting the records, thereby determining the decentralization of the record on the network. Data on how often content on the network changes, were collected and investigated. In addition to evaluating records, a search engine was prototyped to show how to integrate the data into a system. A large part of the network was crawled and the rate of change was found to be high. Most of the peers were found to host HTML files. Most content identifiers found were hosted by more than one peer. This means that a search engine needs to be able to support text file formats and revisit peers regularly to be up-to-date with the records.