Blockchain technologies have gradually gained popularity since the beginning of 2010. As of 2018, many companies and financial institutions are redesigning and building new sys-tems with blockchain technologies as major foundation. On paper, the blockchain has nu-merous advantages over the traditional centralized approach, however, this study showed, that there are some large drawbacks, which are associated with usage of blockchain. Themost significant downsides are blockchain’s low performance, enormous cost and highenvironmental impact, compared to traditional client-server based systems. Therefore, the overall goal of this study was to highlight the importance of consider-ing these drawbacks and discuss, how performing of a detailed feature analysis during the design phase, might guide application developers to the correct path, during theimplementation phase of a system, when blockchain is considered being an alternativeto the traditional client-server approach. As the result of this study, it turned out, thatboth client-server and blockchain based approaches do have their respective use casesand disadvantages. A conclusion was drawn, that the best approach would be eitherto use a mix of both technologies, or to use the blockchain as a verification mechanismbehind a client-server backend, in order to improve its data integrity and persistencequality attributes.

With the advent of big data era, there is countless data produced from various kinds of machines every second. These data are used to help people to do studies, produce goods, improve the efficiency of the industrial development, and so on. Especially considering the Internet of things which connects all the smart machines together, the importance of data integrity gets unprecedented attention from us. In order to keep the data integrity, blockchain comes to its birth using its own structure to guarantee the data integrity efficiently. This project is focus on the simulation of data system based on the blockchain in the background of industrial internet of things which is shown in a form of a website with coding language jade and the environment is Node.Js. The main task is to measure the time consumed in the process of block mining under different parameters include data length, nonce, difficulty, sensor number in order to find the correlation between block mining time and different parameters. Thus, the rule about the impact of different parameter on the mining time are concluded. According to the rule I found, the evaluation about scalability, efficiency and safety of this system are given and I also summarize two formulas to calculate the efficiency of block mining. Ethical consideration and future work are addressed in the conclusion part.

A review of digital forensics today shows that it could be exposed to threats jeopardizing the digital evidence integrity. There are several techniques to countermeasure this risk, one of which is the method that involves the use of blockchains. Blockchains use an advanced system to keep the data within it persistent and transparent, which makes it a natural candidate for everything integrity-sensitive. Several blockchain techniques and infrastructures have been described in this study, based on previous studies and other literature work. Interviews and experiments made a comparison between traditional digital forensic methodologies versus blockchains possible in later chapters. The results showed that blockchains could be the answer to securing digital evidence integrity. However, there is still a lot more work to be done before blockchains are ready to be implemented in production systems. The results of the blockchain analysis are presented such that they can be used as an aid to further research, either theoretically or practically, digital evidence blockchains.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-30T15:34:00Z No. of bitstreams: 1 helderluizpalmiericaldas.pdf: 3093758 bytes, checksum: 78e635406e0664df0546fe72eee1988d (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-30T15:37:48Z (GMT) No. of bitstreams: 1 helderluizpalmiericaldas.pdf: 3093758 bytes, checksum: 78e635406e0664df0546fe72eee1988d (MD5) / Made available in DSpace on 2017-05-30T15:37:48Z (GMT). No. of bitstreams: 1 helderluizpalmiericaldas.pdf: 3093758 bytes, checksum: 78e635406e0664df0546fe72eee1988d (MD5) Previous issue date: 2016-03-07 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O Bitcoin é um sistema de pagamento totalmente digital independente de uma entidade centralizadora como bancos ou governos. O projeto foi criado e publicado em 2008 através da Internet. Entretanto apenas em 2009 a rede tornou-se operacional. O Bitcoin é um protocolo de código aberto e uma rede ponto a ponto de participantes que é responsável pelo funcionamento do sistema. Segurança criptográfica, ausência de taxas e de custos de instalação são fatores que convenceram várias empresas do mundo a adotá-lo como alternativa de pagamento. Apesar dos trabalhos acerca da moeda digital, pouco ainda se sabe sobre sua topologia e características, principalmente pela ótica de ciência de redes. Nesse sentido, o presente trabalho apresenta o estudo da dinamicidade de suas principais variáveis no seu funcionamento diário. No decorrer do trabalho são apresentadas duas formas de extração de dados da rede Bitcoin para futuras análises. / Bitcoin is a fully digital payment system independent of a centralized entity like banks or governments. The Bitcoin project was created and published in 2008. In 2009 the Bitcoin P2P network became operational. The Bitcoin is an open source protocol and a peer-topeer network of participants that is responsible for operating the system. Cryptographic security, absence of exogenous rates and of installation costs convinced several companies in the world to adopt it as a payment alternative. Although, there is an increasing amount of work on digital currencies, little is known about Bitcoin its topology and characteristics, particularly from the viewpoint of network science. In this sense, this paper presents the study of the dynamics of its main variables and their daily functioning. During the work we present two forms of network data extraction Bitcoin for further analysis.

Syftet med uppsatsen är att kartlägga vilka verksamheter och organisationer som använder eller kan tänkas använda blockkedjeteknologin i musikbranschen och jämföra deras affärsidéer mot teorin om delningsekonomi. Den tidigare forskningen uppmärksammar styrningsproblematiken, problematik med intäktströmmar och digitaliseringens möjligheter. Blockkedjeteknologin undersöks som en företeelse i form av en fallstudie där fyra verksamhetsanalyser och tre intervjuer med informatörer och kommunikatörer i musikbranschen analyseras. Resultaten visar på nya möjligheter för musikskapare, lyssnare, användare och verksamheter. Möjligheter som snabbare utbetalning av royalties, transparens i utbetalningskedjan samt effektivare möjligheter i hantering av verksdata. Den nya kunskap studien bidragit med kompletterar den tidigare forskningen om styrningsproblematiken i musikbranschen och ger perspektiv på mångfalden av positiva förändringar blockkedjetekniken kan innebära för verksamma inom ljud- och musikproduktion.

This thesis examines how Distributed Ledger Technologies (DLTs) could be utilized in capital markets in general and in the Nordic capital market in particular. DLTs were introduced with the so called cryptocurrency Bitcoin in 2009 and has in the last few years been of interest to various financial institutions as a means to streamline financial processes. By combining computer scientific concepts such as public-key cryptography and consensus algorithms DLTs make it possible to keep shared databases with limited trust among the participators and without the use of a trusted third party. In this thesis various actors on the Nordic capital market were interviewed and their stance on DLTs were summarized. In addition to this a Proof of Concept of a permissioned DLT application for ownership registration of securities was constructed. It was found that all the interviewees were generally optimistic about DLTs potential to increase the efficiency of capital markets. The technology needs to be adopted to handle the capital markets demand for privacy and large transaction volumes, but there is a general agreement among the interviewees that these issues will be solved. The biggest challenge for an adoption of DLTs seem to lie in that of finding a common industry-wide standard.

In this paper, we analyse the relation between financial system and financial crises. Our goal is to find how, on the one hand, changes in the financial system affect the prospects for financial crises and, on the other hand, how the occurrence of financial crises shape the core elements of the financial system. We start by defining the financial crisis from three different perspectives. After it, we present the comprehensive history of financial crises that will allow us to continue by drawing some common patterns that are universal. Universal patterns in crises give us the ground for contemplating on some universal policy responses where we again follow different approaches. Taking into account the specifics of modern times and using the young and promising economy based on the blockchain, we are asking the question is this time different?. Analysis of initial development steps in the digital, trustless world gives us the basis for drawing parallels with the reality and the history. Our results suggest that there are many similarities throughout history and between the real and digital world. Instead of providing an exact answer on the question is this time different we conclude that there is a present strong feeling of Deja vu.

abstract: The lack of fungibility in Bitcoin has forced its userbase to seek out tools that can heighten their anonymity. Third-party Bitcoin mixers utilize obfuscation techniques to protect participants from blockchain analysis. In recent years, various centralized and decentralized Bitcoin mixing implementations have been proposed in academic literature. Although these methods depict a threat-free environment for users to preserve their anonymity, public Bitcoin mixers continue to be associated with theft and poor implementation. This research explores the public Bitcoin mixer ecosystem to identify if today's mixing services have adopted academically proposed solutions. This is done through real-world interactions with publicly available mixers to analyze both implementation and resistance to common threats in the mixing landscape. First, proposed decentralized and centralized mixing protocols found in literature are outlined. Then, data is presented from 19 publicly announced mixing services available on the deep web and clearnet. The services are categorized based on popularity with the Bitcoin community and experiments are conducted on five public mixing services: ChipMixer, MixTum, Bitcoin Mixer, CryptoMixer, and Sudoku Wallet. The results of the experiments highlight a clear gap between public and proposed Bitcoin mixers in both implementation and security. Today's mixing services focus on presenting users with a false sense of control to gain their trust rather then employing secure mixing techniques. As a result, the five selected services lack implementation of academically proposed techniques and display poor resistance to common mixer-related threats. / Dissertation/Thesis / Masters Thesis Computer Science 2020

Nowadays, malware attacks are increasing day by day, and are an ongoing problem for many entities (e.g. companies, institutions). One of the ways to prevent malware is by using tools such as an antivirus. Indeed, antivirus vendors have created databases containing malware data that are used to detect malware. However, the traditional way to store data is filled with many issues due to its centralized structure, which leads to having a single-point-of-failure. This project aims to answer the challenge of having a centralized structure for storing and sharing data through a system architecture using Design Science Methodology. Throughout the project an implementation of the system architecture has been developed, which lead to having a prototype named HuntChain. It is an on-demand scanning interface, which introduces a decentralized approach (through Blockchain Technology) for storing and sharing malware data, while still having the possibility to detect malware. This prototype has been evaluated in an artificial environment, which demonstrated the fulfillment of the requirements. The artefact also solves the issue of having antivirus databases overlapping with each other, which is a waste of resources. Finally, HuntChain has been developed with the idea that it has to be available to anyone, where any developer could improve, modify, and/or add new functionalities, therefore, it is available on GitHub as an open-source project.

This thesis deals with cryptocurrencies and the underlying principles they are based on. It describes the blockchain technology and explores various cryptocurrencies that utilize it with the focus on their similarities and differences. The next part analyzes InsightAPI, the existing tool for real-time Bitcoin blockchain exploration. It then describes the proposed solution for the Ethereum blockchain explorer, highlights the implementation details, and shows results of its testing. The created tool allows the user to quickly gather information about desired blocks, users, and transactions of the Ethereum blockchain.