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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

Využití decentralizovaných technologií ve vědecké komunikaci / Utilisation of Decentralized Technology in Scholarly Communication

Krejčiřík, Matěj January 2021 (has links)
This thesis presents a detailed explanation and argumentation of why modern decentralized technologies could be utilized in order to improve scholarly communication on many fronts. The current model of scholarly communication, which is dominated by scientific journals, is analysed together with the current economic models in use. The thesis also briefly investigates peer reviews. It also endeavors to explain how scholarly goods might be perceived from an economic standpoint. Blockchain technology offers functionalities that could potentially solve many problems associated with scholarly communication through decentralization. Both permissioned and permissionless blockchains, their implementations, interesting technical/economic/governance aspects and why they are such a unique match for scholarly needs are thoroughly analyzed and explained. Finally minimal viability criteria suitable for assessment of decentralized scholarly projects are proposed. Existing decentralized applications which try to migrate scholarly communication from a current centralized system to a decentralized one are described and examined through the prism of this framework.
202

Blockchain Technology in the Health Data Ecosystem : A Qualitative Study on the Role of Blockchain for Health Data / Blockkedjeteknologi i ett ekosystem av hälsodata

Paulsrud, Viktor, Snihs, Jakob January 2019 (has links)
During the last few years, there has been increasing interest in making medical records more centered around patients. Empowering the patient more in the care process has proven to increase the quality of care. It can also enable increased data sharing among different actors, where today patient health data is locked into thousands of separate data silos. Meanwhile, growth in portable medical devices and patient-generated health data (PGHD) poses a new source of valuable data which today has limited utilization in clinical settings. In solving these issues of data availability without compromising the privacy of patients, blockchain has been suggested to play an important role through a more patient-centric model of controlling information. The purpose of this study is to investigate how blockchain can solve data availability and security issues in the healthcare system. We explore the research question from a Sweden-specific context by first defining the current state of the Swedish health data ecosystem, and then analyzing how blockchain helps in increasing the availability and security of personal health data. Qualitative methods were used, and data was collected through both a literature review and an interview study where 16 semi-structured interviews were conducted with Swedish governmental agencies, EMR providers, informaticians, as well as blockchain experts. The current issues in data availability and security in the Swedish healthcare system were identified together with the benefits of using blockchain in this context. Our findings suggest that Sweden has already solved many of the problems other countries face, limiting the marginal benefit of using blockchain. However, problems of sharing raw data persist and blockchain has benefits in managing accesses to health data from both regulatory and privacy perspectives. There are also benefits of using the technology for ensuring the quality of PGHD as well as providing increased security for health data. Lastly, we propose and discuss three separate blockchainbased solutions to be used in healthcare. A major contribution to literature lies in finding that system barriers in form of legislation and technical and semantic interoperability are issues that first need to be resolved in order to harvest the full value of using blockchain technology - issues often understated in other papers. We call for future studies to investigate practical use-cases such as small-scale consortiums addressing specific data sets or patient groups to provide proof-of-concept on how the technology performs in terms of cost, integrity, security, and scalability in for personal health data. / Patientdata är i dagsläget spridd i tusentals data-silos i sjukvården. Att involvera patienten i vårdprocessen har visat sig förbättra vårdresultatet, vilket senaste åren ökat diskussioner om att göra hälsodata mer tillgänglig och centrerad kring patienten. Samtidigt växer användandet av portabla medicinska apparater och patient-genererad information snabbt, och utgör nu en ny datakälla som i dagsläget i princip inte utnyttjas i den kliniska kontexten. För att lösa dessa problem och öka tillgängligheten av data utan att äventyra patientens integritet har blockkedjeteknologi föreslagits spela en viktig roll genom en mer patientcentrerad modell av informationsdelning. Syftet med denna studie är att undersöka hur blockkedjor kan lösa problemen med tillgänglighet av sjukvårdsdata inom vårdsystemet. Vi undersöker frågeställningen utifrån en svensk kontext genom att först definiera de existerande problem relaterade till datatillgänglighet och säkerhet i det svenska vårdsystemet, för att sedan analysera blockkedjans roll för att lösa dessa problem. Studien är av kvalitativ natur där datainsamling gjorts genom dels en litteraturstudie, och dels genom en intervjustudie, där 16 semistrukturerade intervjuer genomförts med svenska myndigheter, journalsystems-leverantörer, informatiker samt blockkedje-experter. Nuvarande problem inom datatillgänglighet och datasäkerhet identifierades tillsammans med de fördelar som finns av att använda blockkedjor i sammanhanget. Våra resultat visar att Sverige redan har löst många av de problem många andra länder idag möter, vilket potentiellt minskar den marginella nyttan av att använda blockkedjor. Dock existerar fortfarande problem när det gäller delning av digitala kopior av journaler mellan aktörer, och en blockkedjelösning har fördelar ur både regulatoriska perspektiv och integritetsperspektiv. Vidare finner vi fördelar av att använda blockkedjor för att försäkra kvaliteten av patient-genererad hälsodata, samt för att öka säkerheten i arkitekturer som möjliggör datadelnin. Slutligen föreslår vi och diskuterar tre olika blockkedjelösningar för den svenska sjukvårdssektorn. Ett av huvudbidragen till litteraturen ligger i att identifiera systembarriärer i form av legislativa åtgärder samt teknisk och semantisk interoperabilitet - problem som måste lösas för att till fullo kunna åtnjuta fördelarna av en blockkedjelösning. Vi uppmanar framtida studier att undersöka praktiska användningsområden såsom småskaliga konsortium för att vidare bidra med hur tekniken levererar på frågor kopplade till kostnad, integritet, säkerhet och skalbarhet för personlig hälsodata.
203

Measuring Tokenomics

Lin, Min-Bin 01 June 2023 (has links)
Die Blockchain-Technologie revolutioniert die Interaktion zwischen Menschen durch Peer-to-Peer-Netzwerke, Kryptografie und Konsensalgorithmen. Trustless Trust ermöglicht sichere und transparente Transaktionen ohne Zwischenhändler. Trotz der zunehmenden Beliebtheit von Krypto-Assets und den damit verbundenen „Tokenomics“ hat die Öffentlichkeit immer noch kein umfangreiches Wissen über die Funktionsweisen dieser Technologie, und ein Großteil des Diskurses bleibt spekulativ. Das Hauptziel dieser Arbeit ist, die grundlegenden Prinzipien von Krytowährungen (Cryptos) und Non-Fungible Tokens (NFTs) zu untersuchen sowie eine Korrelation zwischen der Technologie und ihren Auswirkungen auf die Wirtschaft aus statistischer und wirtschaftlicher Sicht herzustellen. Um dieses Ziel zu erreichen, wird in den Kapiteln 2 und 3 der Einfluss der Blockchain-Technologie auf Ökonomie und Funktionsweise von Kryptowährungen anhand ökonometrischer Modelle und Clustering-Techniken untersucht. Kapitel 3 untersucht Kryptowirschaft und Blockchain-Funktionalität anhand empirischer Methoden, insbesondere für Coincreatoren und Investoren. Wir zeigen am Beispiel von Ethereum, dass die wirtschaftliche Leistung von Kryptowährungen durch die Gestaltung der ihnen zugrunde liegenden Blockchain-Technologie beeinflusst werden kann. Kapitel 4 untersucht die partiellen Korrelationen von Bitcoin-Renditen über neun verschiedene Zentralbörsen aus der Perspektive eines hochfrequenten, dynamischen Netzwerks. Die vorgeschlagene MHAR-CM liefert Kovarianzschätzungen, die die Besonderheiten der Kryptomärkte berücksichtigen. Das Kapitel zeigt Spillover- und Third-Party-Risiken zwischen diesen Börsen. Kapitel 5 verwendet eine Hedonische Bewertungsmethode, um den DAI Digital Art Index basierend auf dem NFT-Kunstmarkt zu konstruieren. Ein besonderer Fokus liegt auf der Nivellierung der Auswirkungen von Ausreißern mit einer einstufigen robusten Regressions-Huberisierung und einem dynamic conditional score model. Diese Arbeit verknüpft neue Technologien und Wirtschaft durch statistische Modellierung und Analyse. Durch die Bereitstellung empirischer Belege beobachten wir, wie die Blockchain-Technologie unsere Wahrnehmung von Geld, Kunst und anderen Branchen verändert. / The emergence of distributed ledger technologies, such as blockchain, has revolutionized how individuals interact by enabling "trust-less trust" through peer-to-peer networks, cryptography, and consensus algorithms. This technology eliminates intermediaries and provides secure, transparent transaction methods. However, public understanding of this technology, along with "Tokenomics", remains limited, resulting in speculative discourse. The main objective of this thesis is to investigate the fundamental principles of cryptocurrencies (cryptos) and non-fungible tokens (NFTs) and establish a correlation between the technology and its economic impact from statistical and economic perspectives. To achieve this, Chapters 2 and 3 explore the influence of blockchain technology on the economic and functional performance of cryptos using econometric models and clustering techniques. Chapter 3 presents an empirical framework that offers insights to coin creators and investors regarding the interplay between cryptonomics, blockchain functionality, and market dynamics. The economic performance of cryptocurrencies, illustrated with Ethereum as an example, is shown to be affected by the design of their underlying blockchain technology. Chapter 4 examines partial correlations of Bitcoin returns across nine centralized exchanges from a high-frequency dynamic network perspective. The proposed MHAR-CM provides reasonable covariance estimates that account for the unique characteristics of crypto markets. This chapter uncovers spillover risk and counterparty risk among these exchanges. In Chapter 5, a hedonic regression approach is employed to construct the DAI digital art index for the NFT art market. Special emphasis is given to mitigating the impact of outliers using one-step robust regression Huberization and a dynamic conditional score model. The DAI index enhances our understanding of this emerging art market and facilitates observation of its macroeconomic trends. This thesis establishes a connection between emerging technologies and the economy through statistical modeling and analysis. By providing empirical evidence, we gain insights into how blockchain technology is transforming our perceptions of money, art, and various industries.
204

Smart contracts for secure vehicular sharing­access systems using blockchain technologies

Qin, Zhangchi January 2022 (has links)
Ongoing research suggests decentralized solutions based on blockchain for vehicle sharing scenario, to solve the fairness and privacy violation issues in centralized platforms. Users can transfer funds and execute decentralized applications, called smart contracts, in these blockchain­based platforms. Among them, several smart contract schemes are designed for the booking and payment functionality, e.g. dPACE [21] and Sc2Share [50]. Renters and vehicle owners can directly interact with these deployed smart contracts and finish booking, driving and payment, combined with existing vehicle access protocols like HERMES [66]. However, current smart contracts for booking and payment only consider to be executed on the root chain, called Layer­1. In this way, the execution waiting times are too long and transaction fees incurred by the blockchain are too high. Such problems in vehicle sharing can be mitigated by executing smart contracts on Layer­ 2 of blockchain, which is an efficient off­chain technology whose purpose is to scale blockchain transaction capacity while retaining the decentralization benefits of the blockchain. This thesis aims to build a smart contract for booking and payment in vehicle sharing scenario, and use different Layer­2 technologies to test it. First, we design an improved smart contract based the Sc2Share’s structure. The improved points are: 1. Store previous renters’ information, including deposit amount and other booking details, to support sustainable usage in each vehicle. 2. Optimize dispute settlement, to handle malicious behaviors in rental process. 3. Add more events emission for better monitoring the state of vehicle. Then, we pick four representative Layer­2 schemes in latest Layer­2 technologies to compare fee costs. Our smart contract is tested on the representative schemes and a comparison between them is sorted out. We follow the whole steps in booking and payment to measure the performance and fee cost between different Layer­2 schemes. Besides, we also execute the smart contract on Layer­1 as a comparison. The result shows that the contract is executed at different costs in different Layer­2 technologies, but the costs are significantly lower and executions confirmation are faster than Layer­1. This implies that our smart contract with Layer­2 technologies can mitigate the problems mentioned before. / Pågående forskning föreslår decentraliserade lösningar baserade på blockchain för rättvisa och integritetsproblem i centraliseradeplattformar. Användare kan överföra pengar och köra decentraliserade applikationer, så kallade smarta kontrakt, i dessa blockchain­baserade plattformar. Bland dem är flera smarta avtalsscheman designade för boknings­och betalningsfunktionaliteten, e.g. dPACE [21] och Sc2Share [50]. Hyresgäster och fordonsägare kan interagera direkt med dessa implementerade smarta kontrakt och avsluta bokning, körning och betalning, kombinerat med befintliga fordonsåtkomstprotokoll som HERMES [66]. Men nuvarande smarta kontrakt för bokning och betalning anses endast utföras på rotkedjan, kallad Layer­1. På så sätt blir exekveringsväntetiderna för långa och transaktionsavgifterna för blockkedjan för höga. Sådana problem i fordonsdelning kan mildras genom att utföra smarta kontrakt på Layer­2 av blockchain, som är en effektiv off­chain­teknologi vars syfte är att skala blockchain­transaktionskapaciteten samtidigt som blockkedjans decentraliseringsfördelar bibehålls. Detta examensarbete syftar till att bygga ett smart kontrakt för bokning och betalning i fordonsdelningsscenariot, och använda olika Layer­2­teknologier för att testa det. Först designar vi ett förbättrat smart kontrakt baserat på Sc2Shares struktur. De förbättrade punkterna är: 1. Lagra tidigare hyresgästers information, inklusive depositionsbelopp och andra bokningsdetaljer, för att stödja hållbar användning i varje fordon. 2. Optimera tvistlösning för att hantera skadligt beteende i uthyrningsprocessen. 3. Lägg till fler händelseutsläpp för bättre övervakning av fordonets tillstånd. Sedanväljer vi fyra representativa Layer­2­scheman i de senaste Layer­2­teknologierna för att jämföra avgiftskostnaderna. Vårt smarta kontrakt testas på representativa system och en jämförelse mellan dem reds ut. Vi följer hela stegen i bokning och betalning för att mäta prestanda och avgiftskostnad mellan olika Layer­2­scheman. Dessutom utför vi också det smarta kontraktet på Layer­1 som en jämförelse. Resultatet visar att kontraktet utförs till olika kostnader i olika Layer­2­teknologier, men kostnaderna är betydligt lägre och utförandebekräftelsen går snabbare än Layer­1. Detta innebär att vårt smarta kontrakt med Layer­2­teknologier kan mildra de problem som nämnts tidigare.
205

Fair NFTs evaluation based on historical sales, market data and NFTs metadata / Rättvis NFTs utvärdering baserad på historisk försäljning, marknadsdata och NFTs metadata

Rigotti, Marcello January 2023 (has links)
Blockchain technology is rapidly growing and with it, the opportunities it brings. Non-fungible tokens (NFTs) are a type of token that represents unique data that can be owned and traded on a blockchain. The NFT market is still in its early stages, making it difficult for newcomers to enter without a solid background and knowledge of the technology. In this study, we aimed to discover if the new information provided by blockchain and NFTs can be used to build better estimation models. We focused on the availability of every single transaction and the attributes attached to NFTs. Our results showed that the availability of each transaction improves the accuracy slightly, while the attributes attached to the NFT greatly improve accuracy. We are confident that with more data over time, the accuracy will continue to improve mainly if the transactions are able to cover almost all the NFTs inside a collection because all the different combinations of attributes will be analyzed. / Blockchain-teknologin växer snabbt och med det, möjligheterna det ger. Non-fungible tokens (NFTs) är en typ av token som representerar unika data som kan ägas och bytas ut på en blockchain. NFT-marknaden är fortfarande i sina tidiga stadier, vilket gör det svårt för nykomlingar att komma in utan en solid bakgrund och kunskap om teknologin. I den här studien ville vi upptäcka om den nya informationen som tillhandahålls av blockchain och NFTs kan användas för att bygga bättre estimeringsmodeller. Vi fokuserade på tillgängligheten av varje enskild transaktion och attributen som är kopplade till NFTs. Våra resultat visade att tillgängligheten av varje transaktion förbättrar noggrannheten något, medan attributen som är kopplade till NFTs förbättrar noggrannheten mycket. Vi är säkra på att med mer data över tid kommer noggrannheten att fortsätta att förbättras främst om transaktionerna är i stånd att täcka nästan alla NFTs inom en samling eftersom alla olika kombinationer av attribut kommer att analyseras.
206

[pt] A UTILIZAÇÃO DE BLOCKCHAIN PARA CONTROLE DA CADEIA DE DISTRIBUIÇÃO DE COMBUSTÍVEIS DERIVADOS: PROPOSTA DE MODELO DE NEGÓCIO / [en] THE USE OF BLOCKCHAIN FOR CONTROLLING THE OIL AND GAS SUPPLY CHAIN: A BUSINESS MODEL PROPOSAL

GUILHERME COPPI DURANTE 26 May 2021 (has links)
[pt] Os problemas relacionados ao controle de qualidade e a fraudes no setor de distribuição de combustíveis são tão antigos quanto o próprio setor. Furto, desvios de qualidade, sonegação fiscal e adulteração de combustíveis são problemas recorrentes e muito prejudiciais para toda a cadeia. Na tentativa de combater estes desvios, as distribuidoras continuamente empenham esforços e recursos financeiros no desenvolvimento de novos procedimentos operacionais e mecanismos de governança. Tais mecanismos de governança visam reduzir o espaço para oportunismo dos envolvidos e aumentar o controle sobre os produtos ao longo da cadeia. Neste contexto, a Blockchain tem se provado uma eficiente tecnologia para a implantação de mecanismos de governança e para o controle de cadeias de suprimentos. Através do uso de contratos inteligentes executados em uma Blockchain privada, este trabalho propõe um modelo de negócio de uma solução tecnológica para o controle da cadeia de suprimentos de combustíveis. Esta solução visa o rastreamento e certificação do volume vendido, desde a distribuidora até o consumidor final, através de pares digitais refletidos na Blockchain. Com isso, pretende-se garantir um controle pleno das distribuidoras sobre a cadeia de suprimentos. / [en] Problems related to quality control and fraud in the fuel distribution sector are as old as the sector itself. Fuel theft, tax evasion and adulteration are recurrent events and very damaging for the entire industry. In an attempt to suppress these deviations, distributors continually commit efforts and financial resources to the development of new operating procedures, new technologies and new governance mechanisms. Such mechanisms aim to reduce the opportunism and to increase control over products throughout the supply chain. In this context, Blockchain has proven to be an efficient technology for the implementation of governance mechanisms and for the control of supply chains. Through the use of smart contracts executed on a private Blockchain, this work proposes a business model of a technological solution for controlling the volumes being transferred through the fuel supply chain. The proposed solution, presented in the form of a business model, aims to track and certify the volume sold, from the distributor to the final costumer through tokenized digital pairs reflected in a Blockchain. With so, it is intended to guarantee full control of the distributors over the supply chain.
207

[en] DESCENTRALIZED FINANCE: OPPORTUNITIES AND RISKS / [pt] FINANÇAS DESCENTRALIZADAS: OPORTUNIDADES E RISCOS

FRANCISCO ADAO DE PAULA ANDRADE 16 August 2022 (has links)
[pt] A principal contribuição deste trabalho é: Discutir os desafios e oportunidades no surgimento das Finanças Descentralizadas. Este trabalho fornece uma visão abrangente dos princípios fundamentais que sustentam as tecnologias Blockchain, como arquiteturas de sistema e algoritmos de consenso distribuído. Em seguida, nos concentramos em possíveis soluções de Blockchain para o setor financeiro, discutindo seus desafios e oportunidades. / [en] The main contribution of this work is: Discuss the challenges and opportunities in the emergence of Decentralized Finance. This work provides a comprehensive overview of the fundamental principles that underpin Blockchain technologies, such as system architectures and distributed consensus algorithms. Next, we focus on possible Blockchain solutions for the financial sector by discussing their challenges and opportunities.
208

P2P Electricity transaction between DERs by Blockchain Technology

Liu, Ruogu January 2018 (has links)
The popularity of blockchain technologies increases with a significant rise in the price of cryptocurrency in 2017, which drew much attention in the academia and industry to research and implement new application or new blockchain technology. Many new blockchains have emerged over the last year in a broad spectrum of sectors and use cases including IOT, Energy, Finance, Real estate, Entertainment, etc.Despite many exciting research and applications have been done, there are still many areas worth investigating, and implementation of the blockchain based distributed application are still facing much uncertainty and challenging since blockchain is still an emerging technology. Meanwhile, the energy sector is under a transition to be digitalized and more distributed. A global technology revolution has disrupted the conventional centralized power system with distributed resources and technologies, like photovoltaic units (PV), batteries, electric mobilities, etc. The citizens then have control of their generation and consumption profiles.The purpose of this master thesis is to explore existing blockchain technology, and smart contracts such as IOTA, NEO, Ethereum Tobalaba, which can be adapted in the energy sector. Within this thesis, blockchain and the smart contract is proposed as a way of building distributed applications for a p2p transaction use case in the energy asset management platform. A design science research methodology is applied for the artifact development and evaluation for the research result. The design was implemented on Ethereum and tested on Tobalaba public network with ether and GAS. The evaluation shows the artifact for the p2p transaction in energy asset management platform fulfill the completeness, and correctness of the design requirement. The result of the performance test on Tobalaba networks shows a correlation between GAS consumption and transaction time.
209

Internationalization strategy choice for micro-multinationals: a development framework / Internationaliseringsstrategi för mikromultinationella företag: ett utvecklingsstrategiskt ramverk

Sanchez Navarro, Gines January 2018 (has links)
Micro-multinational is a relatively new term and there are still very few studies about how micro-multinationals choose their foreign entry market modes when internationalizing. This thesis attempts to add new knowledge filling the gap between the internal resources of a company and the foreign entry market mode selected for its internationalization process. Furthermore, a systematic methodology that combines internal resources with the selection of the foreign entry market mode will be developed with the goal of aligning the competitive advantages of the company along its international structure. The methodology that this research employs will show how to combine the internal resources of the case study company and its needs when internationalizing based on the characteristics of each foreign entry market mode. The first step of the methodology is determining the variables that categorize each foreign entry market mode that companies implement. Then, the application of the Resource-based View will show the possible competitive advantages of the case study company. Lastly, accounting for the requirements that the case study company has when internationalizing, the possible competitive advantages, derived from the Resource-based View, will be combined with the characteristics of each foreign entry market mode to determine effective recommendations for the case study company to implement in its internationalization strategy. The results of this research show that when a company wants to enter into a foreign market, it should evaluate that decision based on its internal resources. Only then will the company be able to exploit its competitive advantages and be successful in the new market. The decision to internationalize is influenced by requirements such as the level of control, commitment, risk and flexibility that the parent company is willing to have in the new foreign market. Hence, these requirements must be taken into consideration carefully during the entire decision process. / Micro-multinationals är en relativt ny term och det finns för tillfället få studier kring hur dessa företag ska bedriva sin utlandsexpansion när de internationaliserar verksamheten. Syftet med denna uppsats är att bidra med ny kunskap kring ämnet och medverka till att fylla kunskapsgapet som existerar i hur man kombinerar företagets interna resurser och valet av internationaliseringsstrategi. Vidare utvecklas en systematisk metodologi som kombinerar interna resurser med valet av internationaliseringsstrategi för att anpassa företagets konkurrensfördelar med dess internationaliseringsprocess. Metodologin som används i denna rapport visar hur interna resurser hos företaget i den aktuella fallstudien kan kombineras med dess behov för internationalisering baserat på egenskaperna hos varje enskild typ av utlandsexpansion. Första steget i metodologin är att avgöra vilka variabler som karaktäriserar varje enskild strategi för utlandsexpansion som företag planerar att implementera. Nästa steg är att applicera en “Resource-based View” som visar de möjliga konkurrensfördelarna för företagen i fallstudien. Slutligen kombineras kraven som företagen har ställt för sin internationalisering samt de konkurrensfördelar som de visades ha enligt “esoruce-based view” med de olika typerna av utlandsexpansion som finns tillgängliga med syftet att avgöra lämpliga rekommendationer för fallstudieföretagen rörande hur de ska gå till väga i sin internationalisering av verksamheten. Resultaten visar att när ett företag vill etablera sig på en utländsk marknad bör de evaluera beslutet med hänsyn till sina interna resurser. Först då kan företaget utnyttja sina konkurrensfördelar och bli framgångsrika på den nya marknaden.  Beslutet av hur internationaliseringen ska gå till påverkas av krav som moderbolaget har för den nya marknaden såsom behov av kontroll, grad av åtagande, risk och flexibilitet. Dessa krav måste tas i noggrann beaktning under hela beslutsprocessen.
210

Trust and verifiable computation for smart contracts in permissionless blockchains

Harz, Dominik January 2017 (has links)
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.

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