While distributed databases offer great promise their decentralized nature poses a number of security and privacy issues. In what ways can parties misbehave? If a database is truly distributed can a malicious actor hide their misdeeds by presenting conflicting views of the database? Can we overcome such deceit and either prevent it by eliminating trust assumptions or detect such perfidy and hold the malicious party to account? We study these questions across two distributed databases: RPKI (Resource Public Key Infrastructure), which is used to authenticate the allocation and announcement of IP prefixes; and Bitcoin, a cryptocurrency that utilizes a permissionless database called a blockchain to track the transfer and ownership of bitcoins. The first part of this dissertation focuses on RPKI and the potential of RPKI authorities to misbehave. We consider the methods, motivations, and impact of this misbehavior and how an RPKI authority can present inconsistent views to hide this misbehavior. After studying the problem we propose solutions to detect and identify such misbehavior. Now we turn our attention to Bitcoin. We look at ways an attacker can manipulate Bitcoin's Peer-to-Peer network to cause members of the network to have inconsistent views of Bitcoin's blockchain and subvert Bitcoin's core security guarantees. We then propose countermeasures to harden Bitcoin against such attacks. The final part of this dissertation discusses the problem of privacy in Bitcoin. Many of the protocols developed to address Bitcoin's privacy limitations introduce trusted parties. We instead design privacy enhancing protocols that use an untrusted intermediary to mix \aka anonymize, bitcoin transactions via blind signatures. To do this we must invent a novel blind signature fair-exchange protocol that runs on Bitcoin's blockchain. This dissertation favors a dirty slate design process. We work to layer protections on existing protocols and when we must make changes to the underlying protocol we carefully weigh compatibility and deployment considerations. This philosophy has resulted in some of the research described in this dissertation influencing the design of deployed protocols. In the case of Bitcoin our research is currently used to harden a network controlling approximately a trillion dollars.

Yes / This paper estimates liquidity dynamics between virtual and real assets from multiple dimensions, namely market capacity, transaction cost and market efficiency. The data covers transaction information of crypto markets and four equity exchanges (US, UK, EU and Japan) between January 2019 and December 2022. The first result shows a two-way liquidity risk feedback loop between virtual and real markets, and the second result confirms dynamic liquidity interactions between them. The US market is identified as a transmitter rather than a receiver of liquidity risk but may not escape cumulative liquidity shocks.

The monetary policies of states and systems built upon them do not naturally allow transactions of a very small value, as the transaction costs exceeds the actual value of the transaction. These types of transactions are called micropayments. This is problematic as it removes the possibility to monetize content that has a valuation that is so low that the costs of the transaction exceeds the value of the content. In this thesis we aim to create a system that allows micropayments to monetize low value content. We do so by developing a design theory based on Gregor and Jones conceptual model for design theories within Information Systems research. The system that we develop will use the end users computational power to generate a value, by running a cryptocurrency miner. We present the background knowledge required to fully understand the presented design theory. Within the design theory, we present a theoretical framework to base systems on that enables micropayments through cryptocurrency mining. We also present a developed proof of work prototype that proves the validity of the theoretical framework. Lastly we discuss our design theory. We conclude that the design theory enables transactions of a very low value, such as 0,0001 \$ cents. Transactions of such small value is not possible with systems built upon states monetary policies. We also conclude that the proposed design theory can be further developed to function independently of cryptocurrency mining. Instead the value for the transaction could be generated through solving complicated problems if institutions are willing to pay for computational power to solve them.

Every time the development of technology enters a new epoch, big changes inthe business and society will follow. Especially for the entrepreneurs, it signifies both opportunities and challenges at the same time. In the next decade, IoT, AI and blockchain will be the main driving forces in the upcoming technological revolution and demonstrate great synergic potential. There is an old saying, “In a strong wind even turkeys can fly”. The company who can seize this chance may become to the next GAFAs (Google, Amazon, Facebook and Apple); whereas those who completely ignores it may be rolled out of the marketeventually. Business model canvas is a very popular method for startups to align the resources and formulate the strategy, which is also the framework used in our research. The main target of this thesis is to demonstrate a thinking method to converge these new technologies in the business models and evaluate the most significant elements in the business planning stage. It could help the future startups to take advantages of the opportunities and overcome the challengesin the new business environment.

The present thesis is focused on speculative behavior of investors in financial markets. More precisely, the thesis consists of five papers and takes a closer look at two speculation driven financial market anomalies, the overreaction hypothesis and the momentum effect, and considers them in two financial markets, cryptocurrency and commodity markets.

Money laundering is believed to have been around since the introduction of money. It is a vast, international problem which challenges law enforcement agencies and legislating authorities, as well as financial institutions and organizations of interest, all over the world. The past few years, something new has snuck up on law enforcement agencies and legislating authorities, namely Blockchain technology and cryptocurrency. This has caused a number of reactions, such as nations and international organizations quickly updating their anti-money laundering regulations. This goes to show how money laundering is constantly evolving, which makes targeting this crime a constant challenge. There is currently a lot of research being conducted on Money Laundering and specifically research on how to tackle the issue. What this study wishes to contribute with is an overview of the recently published (year 2020), available literature on the matter, to facilitate the continuous work on how to best prevent and detect this crime. The aim with this study is to look at already existing literature and to establish what the current focus is when combatting Money Laundering. It is based on three research questions; What are the three main focus’ areas? What are the challenges? How is anti-money laundering regulations tackling cryptocurrency? The method used is a narrative literature review and the search was conducted through Malmö University Electronic Library. Following explicit inclusion and exclusion criteria, the analysis was based on a total of 22 articles. The results show that the focus’ areas’ and challenges are; cryptocurrency and specifically the EU’s fifth anti-money laundering directive, challenges with international cooperation, and lastly, the role of financial institutions and identifying the beneficial owner.

This thesis describes important existing cryptocurrencies and their basis principles. Especially it describes differences between this cryptocurrencies and theid basis principles. Also describes posibilites for analysis of Bitcoin blockchain. Next part describes improvments of tool for blockchain analysis. Futher it describes cryptocurrency analyzing tool, and it's implemented extensions.

Cryptocurrencies are becoming popular and the demand for monitoring transactions inside them increases alongside with it. In this thesis, I describe few of the most widespread cryptocurrencies built on top of a blockchain and how to obtain information of their transactions in order to raise alarms. I discuss existing solutions and describe application Cryptoalarm designed for monitoring transactions involving specific addresses in order to raise alarms. Cryptoalarm scans blockchains of cryptocurrencies such as Bitcoin, Bitcoin Cash, Litecoin, Zcash, Dash, Ethereum and raises alarms about address activities in real-time.

The subject of the thesis is the parallel digital economy created around the monetary innovation called Bitcoin and the interaction between this technology and its users. Bitcoin is a new kind of digital money and a payment system. Transactions are cryptographically verified by users and subsequently recorded in a publicly distributed account book called blockchain. Bitcoin, as an open-source project, has created a worldwide community of Internet-connected users who are further transforming this cryptocurrency by their specific use. Ethnographic research took place during the meetings of the community surrounding the Prague place called Parallel Polis in the period of years 2017-2018 and was subsequently extended to the "online" world. Bitcoin forms the intersection between technology and the economy, and therefore emphasis is placed on exploring the dynamics that this complex phenomenon creates. The work examines the social practices that actors are constantly shaping on the basis of their various motivations through their participation in Bitcoin and the complex ideas connected with it. It examines the visions, attitudes and practices of the "bitcoiners", who support the functioning of this system and allows its very own existence. These ideas are characterized by certain paradoxes and dilemmas...

Bitcoin har framträtt som den mest igenkännbara kryptovalutan sedan igångsättningen 2009 och har vid skrivande tillfälle ett börsvärde på 1,6 biljoner svenska kronor. Detta ihop med den ekonomiska friheten som Bitcoin erbjuder gör att användarantalet ständigt ökar. Likt all ny teknik så tar det tid innan teknologin är fullt utvecklad och anpassad för den bredda massan. I följd av detta kan säkerheten lida vilket kan resultera till ekonomiska förluster. Denna forskningsinsats undersöker vad för åtgärder och strategier som kan användas för att öka säkerheten via en litteraturstudie. Insatsen undersöker även med hjälp av en enkätundersökning ställd till ett Bitcoin-forum om hur användare av Bitcoin hanterar sina privata nycklar. Arbetet visar att det finns åtgärder som bidrar till ökad säkerhet såsom kryptering och multisignatur men att det hänger mycket på vad användarna själva väljer för typ av bäst strategi för deras användningsområde. Enkätundersökning redovisar att majoriteten av användarna gör säkerhetsmedvetna beslut för hur de använder Bitcoin men att en andel nyttjar mindre önskade tillvägagångssätt. / Bitcoin has emerged as the most recognizable cryptocurrency since its inception in 2009 and, at the time of writing has a market capitalization of 165 billion dollars. This together with the financial freedom that Bitcoin offers means that the number of users is constantly increasing. Like all new technology, it takes time for the technology to be fully developed and adapted to the wider mass. As a result, security can suffer which can result in financial losses. This research effort explores what measures and strategies can be used to increase safety through a literature study. The effort also investigates with the help of a survey conducted at a Bitcoin forum on how users of Bitcoin manage their private keys. The work shows that there are measures that contribute to increased security such as encryption and multi-signature but that much depends on what the users themselves choose for the type of best strategy for their area of use. The survey shows that the majority of users make security-conscious decisions about how to use Bitcoin but that aproportion uses less desirable approaches.