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 purpose of this paper is to select the best GARCH-type model for modelling the volatility of Bitcoin, Bitcoin Cash, Litecoin, Dogecoin and Ethereum. GARCH (1,1), IGARCH(1,1), EGARCH(1,1), TGARCH(1,1) and CGARCH(1,1) are used on the cryptocurrencies closing day return. We select the model with the highest Maximum Likelihood and run an OLS regression on the conditional volatility to measure the day-of-the-week effect. The findings show that EGARCH(1,1) model best suits Bitcoin, Litecoin, Dogecoin and Ethereum data and that the GARCH(1,1) model suits best Bitcoin data. The results show a significant presence of day-of-the-week effects on the conditional volatility of some days for Bitcoin, Bitcoin Cash and Ethereum. Wednesday has a significant negative effect on Bitcoin conditional volatility. Friday, Saturday and Sunday are found to be significant and positive on Bitcoin Cash conditional volatility. Finally, Saturday is found to be significant and positive on Ethereum conditional volatility.

In recent years, blockchain has received more attention in different areas wheredifferent chains show unique properties. Society has been strongly affected by thegrowth of technology and digitalization. Despite the success, the banking system is ina stagnant state in the development of the transaction system. Smart contracts havemore significant potential to be used against blockchain. The contract does not requiremanual handling but could operate independently during all hours of the day. Inaddition, limit them by being applied solely to enable an overview of completedtransactions. A challenge seen with implementing the technology from the bank'sperspective is a new type of form of cooperation. If Ethereum succeeds in proving itselfin its Proof of stake model, there is great potential for a more significant part of thebanking industry to start using smart contracts. The purpose of the study was toinvestigate the effects of implementing smart contracts in a dynamic transaction systemover time. Data obtained from interviews and literature study was the basis formodeling the system. The study aimed to carry out simulations to then be able toevaluate the effects. According to the interviews, blockchain is seen more as a tool tosolve particular problems. The simulations show how the entities in the system areaffected over time when the technology smart contracts are applied.

The software supply chain constitutes all the resources needed to produce a software product. A large part of this is the use of open-source software packages.Although the use of open-source software makes it easier for vast numbers of developers to create new products, they all become susceptible to the same bugs or malicious code introduced in components outside of their control.Ethereum is a vast open-source blockchain network that aims to replace several functionalities provided by centralized institutions.Several software clients are independently developed in different programming languages to maintain the stability and security of this decentralized model.In this report, the software supply chains of the most popular Ethereum clients are cataloged and analyzed.The dependency graphs of Ethereum clients developed in Go, Rust, and Java, are studied. These client are Geth, Prysm, OpenEthereum, Lighthouse, Besu, and Teku.To do so, their dependency graphs are transformed into a unified format.Quantitative metrics are used to depict the software supply chain of the blockchain.The results show a clear difference in the size of the software supply chain required for the execution layer and consensus layer of Ethereum.Varying degrees of software diversity are present in the studied ecosystem. For the Go clients, 97% of Geth dependencies also in the supply chain of Prysm.The Java clients Besu and Teku share 69% and 60% of their dependencies respectively.The Rust clients showing a much more notable amount of diversity, with only 43% and 35% of OpenEthereum and Lighthouse respective dependencies being shared. / Mjukvaruleverantörskedjan sammanfattar
all resurser som behövs för att producera en mjukvaruprodukt.
En stor del av detta är användningen av öppen källkod. Trots att
användningen av öppen källkod tillåter snabb produktion av nya
produkter, utsätter sig alla som använder den för potentiella bug-
gar samt attacker som kan tillföras utanför deras kontroll. Ethere-
um är ett stort blockkedje nätverk baserad på öppen källkod som
försöker konkurrera med tjänster som tidigare endast erbjudits
av centraliserade institutioner. Det finns flera implementationer
av mjukvaran som implementerar Ethereum som alla utvecklas
oberoende av varandra i olika programmerings språk för att öka
stabiliteten och säkerheten av den decentraliserade modellen. I
denna rapport studeras mjukvaruleverantörskedjorna av de mest
populära klienterna som implementerar Ethereum. Dessa utveck-
las i programmeringsspråken Go, Rust, och Java. Dom studerade
klienterna är Geth, Prysm, OpenEthereum, Lighthouse, Besu, och
Teku. För att genomföra studien transformeras klienternas mjuk-
varuleverantörskedjor till ett standardiserat format. Kvantitiva
mått används för att beskriva dessa leverantörskedjor. Resultaten
visar en stor skillnad i storlek av leverantörskedjor för olika
lager i Ethereum. Det visas att det finns en varierande mångfald
av mjukvara baserat på de språk som klienter är utvecklade med.
Leverantörskedjorna av Go klienter sammanfaller i princip fullt,
medan de av Java klienter sammanfaller med en stor majoritet,
och de av Rust klienter visar på mest mångfald i mjukvarupaket. / Kandidatexjobb i elektroteknik 2022, KTH, Stockholm

The IoT offers enormous potentials thanks to its Widespread adoption by many industries, individuals, and governments, leading explosive growth and remarkable breakthroughs that have made it a technology with seemingly boundless applications. However, the far-reaching IoT applications cum its characteristic heterogeneity and ubiquity come with a huge price for more security vulnerabilities, making the deployed IoT systems increasingly susceptible to, and prime targets of many different physical and cyber-attacks including insider attacks, thereby growing the overall security risks to the systems. This research, which focuses on addressing insider attacks on IoT, studies the likelihood of malicious insiders' activities compromising some of the security triad of Confidentiality, Integrity and Availability (CIA) of a supposedly secure IoT system with implemented security mechanisms. To further establish the vulnerability of the IoT systems to the insider attack being investigated in our research, we first produced a research output that emphasized the need for multi-layer security of the overall system and proposed the implementation of security mechanisms on components at all layers of the IoT system to safeguard the system and ensure its CIA. Those conventional measures however do not safeguard against insider attacks, as found by our experimental investigation of a working IoT system prototype. The outcome of the investigation therefore necessitates our proposed solution to the problem, which leverages the integration of distributed edge computing with decentralized Ethereum blockchain technology to provide countermeasures that preserve the Integrity of the IoT system data and improve effectiveness of the system. We employed the power of Ethereum smart contracts to perform integrity checks on the system data logically and take risk management decisions. We considered the industry use case of Downstream Petroleum sector for application of our solution. The solution was evaluated using datasets from different experimental settings and showed up to 86% accuracy rate. / Government of the Federal Republic of Nigeria through the Petroleum Technology Development Fund (PTDF) Overseas Scholarship Scheme (OSS)

目前，因應不同需求與應用情境的各式電子發票系統已被建立。儘管電子發票系統、區塊鏈技術與其相關的文件及平台已經存在，許多研究學者及廠商仍希望推展此技術並應用於其它領域。 本研究的目的在以區塊鏈技術為基礎建構電子發票平台，希望提出一種區塊鏈技術的新應用情境。首先，透過資訊計量學的方法分析980篇電子發票及區塊鏈的相關文獻以了解電子發票及區塊鏈的發展；接著，探討比特幣(Bitcoin)與區塊鏈(Blockchain)間的重要觀念與技術；最後，利用區塊鏈技術中的一種以太坊(Ethereum)來建立電子發票平台。 本研究中六項建構電子發票系統的需求如資料完整性、可驗證性、可用性、可稽核性、不可否認性與可溯源性可被達成。此架構不僅適用於發行一般的消費性電子發票更適用於向企業提供短期資金借貸如發票融資的應用情境。未來，在不同的實作需求下，將可探討整合區塊鏈另一項技術開放鏈(Openchain)以建立混合公開與私有節點的應用。 / Different e-invoice systems are designed to meet different needs and application scenarios. Although these systems areuseful and readily available, researchers and businesses hope to be able to expand the coverage of e-invoice systems using Blockchain technologies. This study proposes an e-invoice system based on Blockchain technologies which shows anotherapplication scenario of Blockchain technology and e-invoice system. First, a review of about 980 publicationson e-invoicing and Blockchain was carried outwithinformetrics used for further analysis so as to better understandthe development of e-invoice and Blockchain technologies. Second, the concepts and mechanisms of Bitcoin and Blockchain technologies were reviewed. Finally, an e-invoice system based on Ethereumwas proposed. The proposed system meets the six needs of an e-invoice system: integrity, authenticity, availability, auditability, non-repudiation and traceability. It is not only suitable for issuing general invoices but also can play a role in further invoicing applications such as invoice financing as well as agri-food supply chain traceability. In the future, Openchain or hybrid Blockchain infrastructure that combines public and private nodes can be consideredfor use in this proposed e-invoice system.

現行醫療保險理賠申請流程相當繁複，被保險人需要向醫療機構申請診斷證明，填具理賠申請書向保險公司提出理賠申請，再由保險公司進行審核。若遇到無法從診斷書直接審核之個案，保險公司需先取得被保險人簽署之調閱病歷同意書後，方能至醫療機構調閱病歷，以利後續理賠審核。這樣的流程，對保險公司來說，需耗費大量人工成本；對被保險人來說，則也有資訊不夠透明的疑慮。 區塊鏈的運作有著公開透明，且難以造假的不可否認性。智能合約是在區塊鏈平台上執行的協議落實程式，既能確保程式不會被竄改，又可保留所有執行紀錄。若能透過這些特性來做為醫療保險理賠傳遞訊息的媒介，除了能提昇保險公司審核流程的時效性，被保險人也能獲得公開透明的資訊。 本論文提出了一套基於智能合約來實現快速醫療保險理賠的方案，我們在以太坊上實作智能合約，我們的方案除了能改善現有的問題，也建構出一套公開透明，且兼顧病人隱私的理賠系統，並考量實際狀況，讓保險公司的業務邏輯可以重用，在理想與現實之間取得一個適當之平衡點。 / Current medical insurance claims application process is complex. It requires the insured to apply for medical diagnosis, and to fill out an application form to the insurance company. The insurance company then reviews the case. If they are unable to approve the claims, they must first obtain the consent form from the insured in order to access to his or her medical records to facilitate subsequent claims review. Throughout the process, the insurance company needs to pay a lot of labor costs; while the insured will have many concerns of information transparency. Blockchain operates in an open and transparent manner and maintains its data in a tamper-free way. Smart contracts are programs executed on a blockchain platform to enforce an agreement such that the program will not be tampered with, and all records of execution will be kept from modification. These characteristics of a smart contract make it very good as a tool for streamlining the medical insurance claims process, as it will greatly reduce the human efforts involved on the insurance company side while increase the information transparency from the perspective of the insured. This thesis presents a smart contract based solution for streamlining the medical insurance claims process. We design and implement the con-tract on the Ethereum platform. In addition to improving the existing problems, our solution builds an open and transparent claims system that takes into account the patient privacy and the practical requirement of re-using the existing claims processing system of the insurance company, thus achieving a proper balance between the ideal and reality.

With the invention of the cryptocurrency Bitcoin in 2009, the world's first blockchain application was developed. While academic research gradually begins to investigate cryptocurrencies more closely and attempt to understand their functioning, technology is rapidly evolving and ecosystems grow exponentially. The research is still scattered and chaotic and has not produced common guidelines. Therefore, the question remains: how sustainable cryptocurrencies and their digital ecosystems are.Only a few models and frameworks take a holistic view on digital sustainability. Only two frameworks were identified that take distributed ledger technologies (blockchain) or cryptocurrencies into consideration: the three governance strategies for digital sustainability of Linkov et al. (2018) and 10 basic conditions of sustainable digital artifacts according to Stuermer, Abu-Tayeh and Myrach (2016). These two frameworks were combined into a new integrated sustainability framework for cryptocurrencies. The developed integrated sustainability framework consists of four dimensions and 12 categories.Existing secondary data, self-conducted social media interviews and practical insights gained through an ASIC mining experiment were used to fill the framework with sufficient data. It confirms Bitcoin's sustainability problems in energy consumption and scalability, highlights Ethereum's great potential as a blockchain platform and explains the higher scalability and faster payment of Ripple and IOTA.While 2017 marked the temporary peak of the cryptocurrency hype, 2018 was a transformative year in which the leading cryptocurrencies were increasingly occupying more specialised niches.

Blockchain at the European Level Abstract The objective of this master thesis is to provide a basic overview of the blockchain technology, its features and its potential utilization, including an overview of European legal regulations that might be applicable to the technology, under certain conditions. In the first chapter, the master's thesis sets forth the legal framework of the EU primary law that establishes or can establish the EU's competence to act in the matters of blockchain technology, depending on its legal qualification (especially in the context of the internal market - namely the free movement of services and capital). The second and third chapters provide essential description of features of blockchain and cryptocurrency and related services. A more detailed description is provided in Annexes I-IV of this thesis. Further, the legal status and applicable regulation of cryptocurrencies are assessed at the European and national levels and in terms of other global jurisdictions. The assessment also includes the recent CJEU's judgment in the case Hedqvist, according to which bidirectional exchange services (purchase of cryptocurrency for fiat currency and vice versa) are to be exempted from VAT obligation under the VAT directive. In line with the CJEU's reasoning and the Advocate General's...

Cryptocurrencies are a cryptography based technology, that has increased massively in popularity in recent years. These currencies are traded on markets that specialize in cryptocurrency trade. There, you can trade one cryptocurrency for another, or buy one with real world money. These markets are quite volatile, meaning that the price of most cryptocurrencies swing up and down a lot. The largest cryptocurrency is Bitcoin, but there is also more than 1500 smaller ones, that goes by the name alternative coins, or altcoins. This thesis will try to find out if it is possible to make accurate predictions about the future price of the altcoin Ethereum, and also see if Bitcoin may have some influence over the price of the selected altcoin. The predictions were made with the use of an artificial neural network, an LSTM network, that was trained on labeled data from 2017. The predictions were then made in intervals of one hour ahead, six hours ahead, and one day ahead through early 2018. The predictions showed that it is possible to make somewhat accurate predictions about the future. The predictions that were made one hour ahead were more accurate than both the six hours ahead predictions and the full day ahead predictions. By comparing the loss rates of the neural networks that were only trained on Ethereum, with the loss rates of the networks that trained on both Bitcoin and Ethereum, is was made clear that training on both cryptocurrencies did not improve the prediction accuracies.