Blockchains address trust through cryptography and consensus. Bitcoin is the first digital currency without trusted agents. Ethereum extends this technology by enabling agents on a blockchain, via smart contracts. However, a systemic trust model for smart contracts in blockchains is missing. This thesis describes the ecosystem of smart contracts as an open multi-agent system. A trust model introduces social control through deposits and review agents. Trust-related attributes are quantified in 2,561 smart contracts from GitHub. Smart contracts employ a mean of three variables and functions and one in ten has a security-related issue. Moreover, blockchains restrict computation tasks. Resolving these restrictions while maintaining trust requires verifiable computation. An algorithm for verifiable computation is developed and implemented in Solidity. It uses an arbiter enforcing the algorithm, computation services providing and verifying solutions, and a judge assessing solutions. Experiments are performed with 1000 iterations for one to six verifiers with a cheater prior probability of 30%, 50%, and 70%. The algorithm shows linear complexity for integer multiplication. The verification depends on cheater prior probability and amount of verifiers. In the experiments, six verifiers are sufficient to detect all cheaters for the three prior probabilities. / Blockchains adresserar tillit genom kryptografi och konsensus. Bitcoin är den första digitala valutan utan betrodda agenter. Ethereum utökar denna teknik genom att möjliggöra agenter i blockchain, via smart contracts. En systemisk förtroende modell för smart contracts i blockchains saknas emellertid. Denna avhandling beskriver ekosystemet för smarta kontrakt som ett öppet multi-agent system. En förtroendemodell introducerar social kontroll genom inlåning och granskningsagenter. Tillitrelaterade attribut kvantifieras i 2,561 smart contracts från GitHub. De använder ett medelvärde av tre variabler och funktioner med en av tio som har en säkerhetsre-laterad fråga. Dessutom blockchains begränsa beräkningsuppgifter. Att lösa dessa begränsningar samtidigt som du behåller förtroendet kräver kontrollerbar beräkning. En algoritm för verifierbar beräkning utvecklas och implementeras i Solidity. Den använder en arbiter som tillämpar algoritmen, computation services som tillhandahåller och verifierar lösningar och en judge som bedömer lösningar. Experiment utförs med 1000 iterationer för en till sex verifierare med en snyggare sannolikhet för 30%, 50% och 70%. Algoritmen visar linjär komplexitet för heltalsmultiplicering. Verifieringen beror på fuskans tidigare sannolikhet och antal verifierare. I experimenten är sex verifierare tillräckliga för att detektera alla cheaters för de tre tidigare sannolikheterna.

Internet of Things (IoT) means that physical objects will be able to interact and communicate via embedded systems. This will lead to a distributed network of devices that can communicate with both humans and each other. One application area is in improving supply chain management. The goal in supply chains is to move a product or a service from the producer to the customer as efficient as possible. Implementation of IoT will have many benefits but it also raises security issues that can affect integrity, security and privacy for both individuals and companies. In 2009, Satoshi Nakamoto created bitcoin and more importantly, blockchain. Blockchain is a ledger of facts, data is not stored in only one network with a common processor, but it is distributed among all the clients on the network. This technology may be a solution to some problems that IoT are facing. This paper looks into up to date research of blockchain and IoT with the purpose to study blockchain as a potential solution to secure IoT data management within supply chains. Both blockchain and IoT are relatively new research areas with little existing research, which support our use of a qualitative inductive method. Semi-structured interviews, which will be further explained in the methodology section, have been conducted with people working within the fields of blockchain, IoT and supply chain. The result indicates that blockchain can be used to secure data management within any given supply chain that uses IoT technology, but blockchain should be seen as a tool, and not as a complete solution. Many of the security issues within IoT are related to the devices and blockchain will not be able to provide a solution to these problems. Blockchain can however be used for handling information, securing identities, traceability of goods, transactions being made without human interaction, automated storage management and time stamped actions to name some examples. There are still barriers to make these benefits work in reality but there is a lot of research currently on-going, trying to make it happen.

The thesis begins by describing the current problems in the fragmented world of music copyrights indicating musicians are not being paid accurately due to lack of transparency in the calculation of royalties and this lead to legal battle. Later we investigate how blockchain technology can alleviate much of the difficulties associated with this complexity. We further explore the legislative and institutional support for the technology necessary for a successful implementation, in form of legislations and governmental projects. We find out that numerous authorities have started voting favourable legislations and recognizing the technology as a valid public ledger. Eventually, we confirm our findings by analysing existing laws.

This thesis paper explores the developing technology blockchain by trying to understand the technology from a technical performance standpoint and also understanding the development process of blockchain networks and applications. The first half of this paper analyzes two research papers, "Bitcoing-NG: A Scalable Blockchain Protocol" and "Untangling Blockchain: A Data Processing View of Blockchain Systems," to understand and explain some of the technical differences and shortcomings of blockchain technologies. The second half of this paper then proceeds to develop a private blockchain network on the Ethereum network and deploy a smart contract on that private blockchain network. This process gives insight into the development of blockchain applications and identifies the struggles blockchain developers face.

KYC(Know Your Customer)是銀行非常重要的一項程序，除了法規上的遵循外，也同時要滿足控制客戶投資風險和防制洗錢的目的，但各銀行重複花費大量的金錢和時間成本在相同客戶KYC資料的收集和驗證上。 區塊鏈是一個採用密碼學及共識演算技術來確保交易資料無法被竄改的分散式帳本系統，被稱為無須中間人的信任機器。 本研究透過區塊鏈做為銀行之信任基礎，在不改變既有的KYC流程下，提出一套”金融KYC平台”架構，讓不同銀行在提供金融服務時，每個客戶的KYC資料收集和驗證的程序只要進行一次。 此平台不使用集中式資料庫，KYC原始資料存放在客戶資料註冊銀行本地資料庫中，銀行透過區塊鏈驗證KYC資料之正確及完整性，並透過區塊鏈上紀錄的相關資訊，進行銀行間的資料的授權及同步作業。本研究實際建置展示了七個金融KYC平台的使用情境，驗證原先的各項程序假設，都能在兼顧安全和效率下完成。 / KYC (Know Your Customer) is a very important procedure for banks not only for regulatory compliance, but also to meet the controls of customer investment risk and the purpose of money laundering control. It takes a lot of money and time in the process of verifying the same customer’s information for each bank. Blockchain is a decentralized ledger platform that uses cryptography and consensus algorithm to ensure that transactional data can not be tampered with, and is known as a “Trust Machine”. Without changing current KYC procedures, this study build a "Banking KYC Platform" based on blockchain technology. And let the KYC validation be only conducted once for each customer between banks. This platform does not use centralized database. The original KYC data is stored in bank's local database. Banks verifiy customer KYC data’s correctness and completeness through blockchain and synchronize them based on the information recorded in blockchain. This study shows the result of verifying seven KYC use cases with this Banking KYC Platform. It is a complete demonstration for reaching the goal of solving security, efficiency and cost reduction problems.

abstract: The coordination of developing various complex and large-scale projects using computers has been well established and is the so-called computer-supported cooperative work (CSCW). Collaborative software development consists of a group of teams working together to achieve a common goal for developing a high-quality, complex, and large-scale software system efficiently, and it requires common processes and communication channels among these teams. The common processes for coordination among software development teams can be handled by similar principles in CSCW. The development of complex and large-scale software becomes complicated due to the involvement of many software development teams. The development of such a software system can be largely improved by effective collaboration among the participating software development teams at both software components and system levels. The efficiency of developing software components depends on trusted coordination among the participating teams for sharing, processing, and managing information on various participating teams, which are often operating in a distributed environment. Participating teams may belong to the same organization or different organizations. Existing approaches to coordination in collaborative software development are based on using a centralized repository to store, process, and retrieve information on participating software development teams during the development. These approaches use a centralized authority, have a single point of failure, and restricted rights to own data and software. In this thesis, the generation of trusted coordination in collaborative software development using blockchain is studied, and an approach to achieving trusted cooperation for collaborative software development using blockchain is presented. The smart contracts are created in the blockchain to encode software specifications and acceptance criteria for the software results generated by participating teams. The blockchain used in the approach is a private blockchain because a private blockchain has the characteristics of providing non-repudiation, privacy, and integrity, which are required in trusted coordination of collaborative software development. This approach is implemented using Hyperledger, an open-source private blockchain. An example to illustrate the approach is also given. / Dissertation/Thesis / Masters Thesis Software Engineering 2020

This diploma thesis deals with the creation of a design for the utilization of blockchain technology in a corporate environment. The main goal of this work is to create a proposal for a business process and its implementation in a specific blockchain platform. The analysis of the current state of the process describes current process and company’s requirements for the functionality of new technology. In the design part of the work, I compared specific blockchain platforms. As a result of this part I chose the most suitable solution for the implementation of my proposal. This chapter further includes the design of a methodology for verifying whether the process is suitable for the implementation of a blockchain technology or not. Moreover, it describes how to proceed when choosing a suitable solution and highlights its key factors.

The main subject of this work is the assessment of electronic voting systems with regard to their required and achieved properties. The goal of this project is designing an electronic voting protocol that satisfies the requirements for privacy protection while also being scalable and fault-tolerant. Existing protocols are examined and compared according to their properties. The design proposed in this work uses smart contracts on blockchain and combines the approaches from the examined solutions. Scalability is achieved by dividing the process of voting between several smart contracts. Each of these contracts carries out the voting in small scale with only a subset of voters and the partial results are then aggregated. The problem of finding a suitable platform for implementation of the proposed protocol is also addressed in this work.

With the internet being the perhaps most important invention in recent time, the introduction of web 3.0 and the blockchain may be considered the most revolutionizing technology since then.A decentralized internet would mean that users can do business with each other in a fast and secure way, without the need for a trusted third party. The possibility of tokenizing digital assets creates a way of representing ownership that has not been a reality until now. NFTs are tokens stored in smart contracts in the blockchain that are transferable between owners and have reached increased popularity in recent years. However, since the technology is still in its infancy, literature covering the topic is scarce and limited. A systematic literature review of the most current and relevant research papers about NFTs allowed for the creation of an initial taxonomy, deconstructing the NFT into its building blocks to serve as a tool for navigating the currently scattered research field. After that, the taxonomy’s suitability was evaluated against modern-day applications of NFTs and expanded appropriately to better describe real-world projects. The contribution of the study is a taxonomy composed of eight main components, both technical and non-technical, describing NFTs. Furthermore, for these eight components, thirty different layouts were identified.

Blockchain, a solution for different parties to reach consensus in a peer­to­peer (P2P) networks, allows us to distribute data across different entities. Many areas, including financial, health care, eCommerce, marketing, can benefit from blockchain technology. Influencer marketing also takes benefit from the properties of blockchain technology. Most of the time, social media influencers have an” ideal” body, affecting how theproduct they are advertising looks on them, which results in increased returns inonline shopping. Moreover, existing applications are not involving micro­influencers(10,000 ­ 100,000 followers) in the campaigns that brands have created. In order to tackle the mentioned problems, a blockchain distributed size and fit application framework is proposed in this thesis. The framework offers a possibility for micro influencers to participate in the brands’ campaigns. However, micro­influencers are not directly involved in communication with brands. Instead, macro­influencers (over100,000 followers) play a role as a bridge between micro­influencers and brands by creating sub­campaigns of the brands’ campaigns. With the involvement of micro influencers in the proposed framework, they also share their pictures with the same outfit (different body sizes and shapes), which gives potential buyers a better idea of how the same outfit would look on them before they decide to buy. The proposed solution is implemented with smart contracts using Solidity and tested in the Ropstentest network. Testing the smart contract in the Ropsten test network shows that the proposed solution is feasible in terms of financial costs. The proposed framework is not limited to giving the possibility to only brands to advertise products, but it also offers macro­influencers and potential micro­influencers an opportunity to earna reward in exchange for promoting the products of brands. The whole process starting from applying for a campaign to claiming reward is handled without manual intervention. / Blockchain, en lösning för olika parter för att nå konsensus i ett peer­to­peer­nätverk(P2P), låter oss distribuera data över olika enheter. Många områden, inklusiveekonomi, hälsovård, e­handel, marknadsföring, kan dra nytta av blockchain­teknik.Influencer­marknadsföring drar också nytta av blockchain­teknikens egenskaper.För det mesta har påverkare på sociala medier en ”idealisk” kropp som påverkarhur produkten de annonserar ser ut på dem, vilket resulterar i ökad avkastning ionline­shopping. Dessutom involverar befintliga applikationer inte mikroinfluencer(10 000 ­ 100 000 följare) i de kampanjer som varumärken har skapat. För atthantera de nämnda problemen föreslås en blockchain­distribuerad applikationsrami denna avhandling. Ramverket erbjuder en möjlighet för mikroinfluencer attdelta i varumärkets kampanjer. Mikroinfluencer är dock inte direkt inblandade ikommunikation med varumärken. Istället spelar makroinfluencer (över 100 000följare) en roll som en bro mellan mikroinfluencer och varumärken genom att skapaunderkampanjer av varumärkets kampanjer. Med deltagande av mikroinfluenceri det föreslagna ramverket delar de också sina bilder med samma outfit (olikakroppsstorlekar och former), vilket ger potentiella köpare en bättre uppfattning omhur samma outfit skulle se ut på dem innan de bestämmer sig för att köpa . Denföreslagna lösningen implementeras med smarta kontrakt använder Solidity och testasi Ropsten­testnätverket. Att testa det smarta kontraktet i Ropsten­testnätverket visaratt den föreslagna lösningen är genomförbar när det gäller finansiella kostnader.Den föreslagna ramen är inte begränsad till att ge endast varumärken möjlighetatt marknadsföra produkter, men den ger också makroinflytande och potentiellamikroinfluencer möjlighet att tjäna en belöning i utbyte för att marknadsföraprodukter från varumärken. Hela processen från att ansöka om en kampanj till attfå belöning hanteras utan manuellt ingripande