Blockchain technology is a booming new field in both computer science and economicsand other use cases than cryptocurrencies are on the rise. Permissioned blockchains are oneinstance of the blockchain technique. In a permissioned blockchain the nodes which validatesnew transactions are trusted. Permissioned blockchains and distributed databasesare essentially two different ways for storing data, but how do they compare in terms ofperformance? This thesis compares Hyperledger Fabric to Apache Cassandra in four experimentsto investigate their insert and read latency. The experiments are executed usingDocker on an Azure virtual machine and the studied systems consist of up to 20 logicalnodes. Latency measurements are performed using varying network size and load. Forsmall networks, the insert latency of Cassandra is twice as high as that of Fabric, whereasfor larger networks Fabric has almost twice as high insert latencies as Cassandra. Fabrichas around 40 ms latency for reading data and Cassandra between 150 ms to 250 ms, thusit scales better for reading. The insert latency of different workloads is heavily affected bythe configuration of Fabric and by the Docker overhead for Cassandra. The read latency isnot affected by different workloads for either system.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-06-22T17:04:20Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Utilizando o Protocolo Bitcoin para Condução de Computações Multilaterais Seguras e Justas.pdf: 1665447 bytes, checksum: 2ff437be55e080c80d97e0d6582cb360 (MD5) / Made available in DSpace on 2016-06-22T17:04:20Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Utilizando o Protocolo Bitcoin para Condução de Computações Multilaterais Seguras e Justas.pdf: 1665447 bytes, checksum: 2ff437be55e080c80d97e0d6582cb360 (MD5) Previous issue date: 2016-02-02 / Suponha que dois milionários desejam descobrir quem é o mais rico sem que, para isso, um descubra o valor da fortuna do outro. Esse problema pode ser facilmente resolvido se ambos concordarem sobre um juiz a quem eles possam confiar a tarefa de calcular a resposta sem quebrar a privacidade de nenhum dos dois. O desafio, no entanto, é substituir esse juiz por uma interação multilateral, ou protocolo, que alcance o mesmo grau de segurança. Isso significa conduzir uma computação multilateral segura. Esse exemplo é conhecido como o problema dos milionários de Yao e foi proposto por Andrew Yao em um dos primeiros esforços para desenvolver uma forma geral de se conduzir computações multilaterais seguras. Desde lá, na década de 1980, vários avanços foram feitos nesse sentido e, hoje, já é um resultado bem estabelecido que qualquer função multilateral pode ser computada de maneira segura. Esse importante resultado, no entanto, vem com uma importante ressalva: a justiça não pode ser alcançada de maneira geral. Entende-se por justiça a garantia de que, no final de uma computação, ou todos os participantes recebem suas respostas ou nenhum deles recebe. Motivadas por esse resultado de impossibilidade, várias definições alternativas de justiça foram concebidas. Uma delas considera uma computação como sendo justa se os participantes que agirem desonestamente forem monetariamente penalizados. Ou seja, se alguns participantes receberem o resultado da computação e privarem os demais de receberem, então esse conluio é penalizado e os demais participantes, compensados. Com essa definição, uma computação justa pode ser vista como o cumprimento de um contrato, no qual cada participante se compromete a agir honestamente ou a pagar uma multa. Sob essa perspectiva, trabalhos recentes mostram como criptomoedas podem ser utilizadas para escrever esses contratos e, portanto, servir para condução de computações multilaterais seguras e monetariamente justas. Uma criptomoeda é um sistema monetário que se baseia em princípios criptográficos para alcançar segurança e controlar a taxa de emissão de novas moedas. O Bitcoin, criado em 2008 por Satoshi Nakamoto, foi a primeira realização dessa ideia. Ele se baseia em uma estrutura de dados pública chamada blockchain, que armazena o histórico de todas as transações já realizadas. A segurança da blockchain, incluindo sua não-maleabilidade, é garantida pela dificuldade da prova de trabalho exigida para que novas informações sejam adicionadas nessa estrutura. Cada transferência de moedas no Bitcoin é feita de maneira que um usuário só pode recebê-las mediante a apresentação de uma entrada que satisfaça um script especificado pelo remetente. Contratos escritos através desses scripts se fazem cumprir sem a necessidade de intervenção de uma parte confiável externa. Essa característica é o que faz o Bitcoin ser adequado e atrativo para se conferir justiça para computações multilaterais seguras. Um dos nossos objetivos neste trabalho é a realização de um estudo sobre os resultados que permitem a computação segura de uma função qualquer e dos que estabelecem a impossibilidade de se alcançar justiça de maneira geral. Tentaremos manter o rigor matemático para evitar uma apresentação estritamente panorâmica. Além disso, analisaremos criticamente uma construção proposta para utilizar o Bitcoin como plataforma para condução de computações multilaterais seguras e justas. Por fim, a partir dos pontos positivos e negativos levantados, apresentaremos uma proposta nossa com a mesma finalidade. / Suppose that two millionaires want to find out which one is the richest, but without revealing how much their fortunes are worth in the process. This problem can be easily solved if they trust a judge to compute the desired answer without compromising their privacy. The challenge, however, is to replace such a judge by a multiparty interaction, or protocol, that achieves the same level of security. That is, the challenge is to carry out a secure multiparty computation. The previous example is known as Yao’s millionaires’ problem and was stated by Andrew Yao in one of the first efforts to develop a general algorithm to carry out secure multiparty computations. Since then, in the 1980s, several advances were made to achieve this goal and, nowadays, it is a well-established result that any multiparty function can be securely computed. This important result, however, comes with an important restriction: fairness cannot be achieved in general. Fairness is the guarantee that, at the end of a computation, either all parties receive their outputs or none of them does. Motivated by this impossibility, several alternative definitions of fairness have been proposed. One of them considers a computation to be fair if the dishonest parties are monetarily penalized and the honest ones are monetarily compensated. According to this definition, a fair computation can be viewed as the enforcement of a contract, in which the parties agree on paying a penalty if they misbehave. Recent works have shown how cryptocoins can be used to write those contracts and, therefore, to be used for carrying out secure and monetarily fair multiparty computations. A cryptocoin is a monetary system that relies on cryptographic principles for achieving security and controlling the coin issuing rate. Bitcoin, created in 2008 by Satoshi Nakamoto, was the first practical realization of this idea. In its core, there is a publicly maintained data structure called blockchain, which works as a ledger and stores every transaction ever made. The security of the blockchain, including its non-malleability, is guaranteed by the difficulty of the proof of work required to add new data to it. A Bitcoin transaction can only be redeemed by a user that presents an input satisfying a script specified by the issuer of the transaction. Contracts written on these scripts are enforced without an external trusted third-party to intervene. This makes Bitcoin suitable and interesting to confer monetary fairness to multiparty computations. One of the goals of this work is to present the results that allow any function to be securely computed and the ones that show the impossibility of achieving fairness in general. We will try to present these results with the appropriate mathematical rigor to avoid giving just an overview of them. We will also analyze a recently proposed construction that uses Bitcoin as a platform to carry out fair multiparty computations. Finally, based on its positive and negative points, we will propose a construction with the same goal.

This master thesis explores how blockchain technologies can be utilized within the financial sector with focus on how to store both private and public information on the blockchain. The capital market is looking into ways of cutting down administrative work through streamlining the financial process by using blockchain technologies. Public key encryption together with hash functions and a consensus mechanism make up the basis for creating a shared trustless database system. The thesis was conducted by extensive research concerning cryptographic topics, and a literature study was made to compare existing solutions. This was done in order to come up with a new design which suggests how to utilize blockchain technologies in order to create private transactions. The design solves issues regarding key management and how to handle both private and public information on the blockchain. The proposed design is an extension of Visigon's existing permissioned blockchain, and it introduces different roles within the peer to peer network as well as a concept of having regulating nodes that together with the involved bank's nodes handle the process of private transactions. Private transactions are encrypted by using symmetric keys and thereafter recorded on the blockchain. In conclusion blockchain technology might not be the most suitable database system for banks to keep transactions private. Future solutions should consider the best attributes of blockchain technologies and create a new system with the single purpose of being a tool for the financial market.

Orientador: Wagner Luiz Lourenzani / Resumo: Muito tem sido divulgado sobre o potencial da tecnologia do blockchain, seus benefícios e seu impacto disruptivo em diversas áreas. Entretanto, no âmbito acadêmico, o desenvolvimento dessa temática é incipiente. Embora crescentes, os estudos científicos têm sido publicados sem que se possa estabelecer uma convergência teórica de suas bases de fundamentação, transpondo conceitos e autores. A maioria dos estudos analisados concentra-se no campo teórico e tem sua abordagem fundamentada em conceitos do campo de conhecimento da tecnologia da informação, sem uma abordagem universalista. Nesse contexto, essa pesquisa tem o objetivo de conduzir uma análise baseada na teoria fundamentada em dados da convergência teórica que fundamenta adoção do blockchain na gestão da cadeia de suprimentos. A metodologia esteve baseada em uma revisão sistemática de literatura e da adoção da teoria fundamentada em dados. A partir da integração de nichos de conhecimento foi possível estabelecer uma declaração universalista que converge as abordagens de adoção do blockchain na gestão da cadeia de suprimentos, que transpassa os moldes disciplinares e atinge o plano interdisciplinar, promovendo a abertura de novos campos para aprofundamento do conhecimento. Os resultados dessa pesquisa revelam que a tecnologia blockchain fortalece a performance, a confiança, a transparência e a prestação de contas na gestão da cadeia de suprimentos. Quando identificadas as condições de fragilidade ou incerteza no relaciona... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Much is publicized about the potential of blockchain technology, its benefits and its disruptive impact in several areas. However, in the academic field, the development of this theme is incipient. Although increasingly, scientific studies have been published without being able to define a theoretical convergence of their foundations, transposing concepts and authors. Most of the studies analyzed focus on the theoretical domain and have their approach based on concepts of information technology knowledge, without a universalist approach. In this context, this research aims to conduct an analysis based on grounded theory, of the theoretical convergence that allows the adoption of blockchain in supply chain management. The methodology adopted considers a systematic literature review and grounded theory. From the integration of knowledge niches, it was possible to define a universalist declaration that converges as blockchain application approaches in the management of supply chains, which pass the disciplinary molds and reach the interdisciplinary plan, promoting the opening of new fields for the improvement of the knowledge. The results of this research reveal that blockchain technology strengthens performance, trust, transparency and accountability in supply chain management. When identified as conditions of fragility or uncertainty in the relationship of the parts of this chain, and these main social, organizational or technological factors, or the blockchain can be used as ... (Complete abstract click electronic access below) / Mestre

Under de senaste åren har blockchain-tekniken fått mer och mer uppmärksamhet. Det har visat speciella fördelar i digital valuta, eftersom det distribueras och dess data inte kan ändras. Med fler länder som presenterar idén om kraftsysteminnovationen har ett stort antal distribuerade kraftkällor dykt upp. Nätanslutningen för dessa distribuerade kraftkällor leder till instabil nätdrift och ökar svårigheten att hantera kraftigt. Därför finns det ett akut behov av en lösning som kan realisera direkt transaktion av distribuerad kraftförsörjning. Denna artikel gör en fördjupad analys av blockchain-tekniken, inklusive hasalgoritm, konsensusmekanism, Merkle-träd, smart kontrakt etc. Och sedan studeras Ethereum och smarta nät. Den här artikeln realiserar automatisering och intelligens för mätning av eltransaktioner genom smart kontraktsteknik som tillhandahålls av Ethereum. En blockchain privat kedja skapas och sedan distribueras det smarta kontraktet i den privata kedjan. Med fördelarna med blockchaintekniken ovan kommer lagring av kraftdata och krafttransaktioner att vara mer trovärdig och mer transparent. Sammantaget designar och bygger detta papper ett smart grid-system baserat på blockchain-smarta teknik. Systemet kan inte bara användas för smarta nätsystem utan även för andra energisystem. Denna artikel ger en referens för tillämpning av blockchain-teknik. / In recent years, blockchain technology has received more and more attention. It has shown special advantages in digital currency, because it is distributed and its data cannot be altered. With more countries put forward the idea of the power system innovation, a large number of distributed power sources have emerged. The grid connection of these distributed power sources will lead to unstable grid operation and greatly increase the difficulty of management. Therefore, there is an urgent need for a solution that can realize direct transaction of distributed power supply. This article makes an in-depth analysis of the blockchain technology, including hash algorithm, consensus mechanism, Merkle tree, smart contract, etc. And then the Ethereum and smart grids are studied. This article realizes automation and intelligence of the electricity transaction measurement through the smart contract technology provided by Ethereum. A blockchain private chain is created and then the smart contract is deployed into the private chain. With the advantages of blockchain technology aforementioned, the storage of power data and the power transactions will be more credible and more transparent. All in all, this paper designs and builds a smart grid system based on the smart contract technology of blockchain. The system can be used not only for smart grid systems but also for other energy trading systems. This article provides a reference for the application of blockchain technology.

Nubo is a broker-less and decentralized edge cloud marketplace that provides APIexposure for integration between entities of the marketplace, i.e., service providers and customers of edge cloud. The core functionalities of this marketplace are implemented by using Hyperledger Fabric blockchain. Some of the marketplace features are Subscription to a service, Service registration, Service onboarding, and Application onboarding. Although it has many features, the Nubo marketplace does not provide performance assurance to the customers, which is one of the main reasons for the lack of trust between the service providers and customers. The SLA management can resolve this issue, and it builds a trusted environment in the marketplace. SLA management facilitates the generation of a formal contract between the service provider and the customer, in which the parties agree on the service’s anticipated performance level (measured in terms of QoS indicators). It also involves consequences in the form of a penalty when the expectations are not achieved during the contract period. One of the challenges in SLA management in the marketplace is to describe the SLA considering different edge cloud characteristics such as multi-parties, network services, etc. In this thesis, we studied the specific requirements for describing the edge cloud SLA and SLA intent, and then we proposed TOSCA models that can be used to describe SLA and SLA intent in the marketplace. In the end, we evaluated the proposed models with the help of an edge cloud use case. / <p>Due to the covid pandemic, I made my presentation online.</p>

Syftet med denna studie var att förstå kriterier, barriärer, kostnader och fördelar som är förknippade med implementering av blockchain-teknik, och utifrån detta utforska hur blockchain-teknik kan förbättra BPM. Studien är av kvalitativ karaktär och gjordes sekventiellt genom att först genomföra en omfattande tvärvetenskaplig litteraturöversikt och därefter intervjua personer med erfarenhet från blockchain-teknik. Analysen gjordes med både en induktiv och deduktiv ansats där tematisk analys tillämpades. Resultaten från studien visar att blockchain-teknik kan minska transaktionskostnader, förbättra avstämning och verifiering, förbättra samarbetsprocesser och skapa förtroende och öppenhet samtidigt som de stöder organisationer med styrning av datasäkerhet, korrekthet av data, och minskade IT-kostnader till följd av förbättrad hantering med säkerhetskopiering av data, servrar och lagring. Stort fokus ligger för tillfället på smarta kontrakt där integrering av affärslogiken tillsammans med en förbättrad databasstruktur möjliggör förbättrat samarbete och automatisering av standardiserade affärsprocesser. Resultaten indikerar också brist på blockchain-ingenjörer, vilket påverkar utveckling och tillväxt. Studien belyser ett behov av ytterligare implementeringsstudier och att bättre skilja mellan de olika blockchain-typerna och de problem de kan lösa. Säkerhet, hållbarhet och interoperabilitet nämns ofta som utmaningar i den pågående diskussionen om blockchain. Detta är inte unikt för blockchain-teknik och mer nyanserade förklaringsmodeller krävs. Blockchain-teknik kan vara framtiden, och kan ersätta befintlig infrastruktur, i slutändan måste organisationer överväga vid vilken tidpunkt de bör börja tänka på att sätta blockchain på sin agenda, med de olika avvägningar som detta innebär. / The purpose of this study was to understand criteria, barriers, costs and benefits that are associated with implementing blockchain technology, and from this explore how blockchain technology can improve BPM. The study is of qualitative nature and was done sequentially by conducting an extensive cross-disciplinary literature review first, and then interviewed people with experience from blockchain technology. The analysis was done with both an inductive and deductive approach by doing a thematic analysis. The results from this study show that blockchain technology can reduce transactional costs, improve reconciliation, improve collaborative business processes and bring trust and transparency while supporting organizations with governance of data security, data consistency and reducing associated IT-costs with managing back-up of data, servers and storage. A lot of focus is currently centered around smart contracts, where incorporating the business logic together with an improved database structure allows for improved collaboration and automation of standardized business processes. The results also indicate a shortage of blockchain engineers, consequently impacting development and growth. The study highlights a need for further implementation studies and to better distinguish between the different blockchain types and the problems they can solve. Security, sustainability and interoperability are often mentioned as challenges in the current discourse on blockchain. This is not unique for blockchain and more nuanced explanation models are required. Blockchain technology may be the future and replace existing infrastructure, ultimately organizations have to consider at what point in time they should start thinking about putting it on their agenda and the associated trade-offs that comes with this. / <p>2021-06-06</p>

This thesis deals with stochastic location routing problem. Multiple stochas- tic and deterministic models are formulated and it is discussed that it is difficult to solve these problems via exact integer programming methods. It is necessary to develop heuristic methods to find a solution of these problems. Multiple ver- sions of these problems are formulated and their properties and possibilities how to solve them are discussed. Therefore, the brand new Blockchain metaheuristic is developed and later used for solving stochastic location routing problem ap- plied on a waste collection problem. As a part of Blockchain metaheuristic we develop the new application of Greedy algorihtm that is used for finding initial solution. The quality of the heuristic algorithm developed by us is presented in a numerical study. 1

To achieve net zero emissions by 2050, a $275 trillion investment is needed, with the private sector playing a significant role. Green corporate bonds are a popular financing method, having grown to 6% of global corporate bonds in 2021. Despite their potential, green bonds face challenges, such as lack of standardization, high costs, and greenwashing risks. Tokenization through Security Token Offerings (STOs) can increase demand and supply for green bonds by enabling fractional ownership, eliminating intermediaries, and improving transparency with blockchain technology and IoT sensors. This drives demand, increases liquidity, and reduces greenwashing risk. STOs also allow smaller investments and finance access for SMEs.This study employs a multi-criteria decision-making model to select a blockchain platform for STOs in green bonds. The process involves identifying platforms, defining features, evaluating suitability, and selecting the platform that best aligns with green bond STO requirements. / För att uppnå netto nollutsläpp till 2050 krävs en investering på 275 biljoner dollar, där den privata sektorn spelar en betydande roll. Gröna företagsobligationer är en populär finansieringsmetod, som växte till 6% av de globala företagsobligationerna 2021. Trots deras potential står gröna obligationer inför utmaningar, som brist på standardisering, höga kostnader och risker med greenwashing. Tokenisering genom Security Token Offerings (STOs) kan öka efterfrågan och tillgången på gröna obligationer genom att möjliggöra bråkägande, elimineramellanhänder och förbättra transparensen med blockkedjeteknik och IoT-sensorer. Detta driver efterfrågan, ökar likviditeten och minskar risken för greenwashing. STO tillåter också mindre investeringar och finansieringsåtkomst för små och medelstora företag.Denna studie använder en flerkriteriemodell för beslutsfattande för att välja en blockkedjeplattform för STO i gröna obligationer. Processen innefattar identifiering av plattformar, definition av funktioner, utvärdering av lämplighet och val av den plattform som bäst överensstämmer med kraven för gröna obligationers STO.

Background: The internet of things (IoT) is transforming industries by enabling data-driven decision-making. IoT play a crucial role in the transition to a Circular Economy of businesses. However, the intrinsic features of the IoT, such as centralization, poor interoperability, and privacy and security vulnerabilities, pose several challenges. Blockchain technology offers potential solutions to these challenges and can enhance traceability and information reliability, while also creating new avenues of interactions and value creation. A combination of these technologies is called Blockchain of Things (BCoT). Additionally, technology such as BCoT and assist the adoption of Circular Economy, a paradigm of sustainable and resource-optimization activities.  Purpose: This study aims to explore the potential challenges of adopting Blockchain of Things and Circular Economy practices, and potential barriers of adopting Blockchain of Things for Circular Economy.  Method: The study uses an explorative-qualitative research method where primary data was gathered through semi-structured interviews. The data was then transcribed and categorized through the use of the Gioia-method, which was then applied to the TOE-framework.   Result: This study finds several barriers regarding Blockchain of Things and Circular Economy, such as lack of standardization, lack of data &amp; information, lack of knowledge, lack of regulations, and finally, slow mind-shift of decision makers.  Conclusion: The results of the study points toward greater systemic challenges of knowledge and standards. Conclusions that can be derived from this are  that industries are still in the early adoption phase of digitalization, which is the reason for a lack of insight and knowledge regarding new technologies. Additionally, identified challenges of a lack of standards, regulations, and know-how regarding Circular Economy showcases a lack of knowledge and confidence in being able to create competitive, sustainable circular activities. / Bakgrund: "Internet of Things" (IoT) är i skedet av att transformera industrier genom att möjliggöra datadriven  bestlutsfattande. IoT spelar även en stor roll i övergången till en Cirkulär Ekonomi av företag. Men flera av IoTs egenskaper såsom centrialisering, samverkan, integretitet, och säkerhet lägger grunden för flera utmaningar.  Blockchain teknologi och dess inbyggda funktioner medgör potentiella lösningar för dessa utmaningar och kan förbättra spårbarhet och pålitlighet av information, samtidigt som den kan skapa nya tillvägagångssätt och värdeskapande. En kombination av IoT och Blockchain kallas för Blockchain of Things (BCoT) Dessutom kan teknik som BCoT  underlätta integration av cirkulär ekonomi, ett paradigm för hållbara och resursoptimerande aktiviteter/handlingar. Syfte: Denna studie strävar till att undersöka de potentiella utmaningarna med att integrera Blockchain of Things och cirkulära aktiviteter, och potentiella hinder för att integrera Blockchain of Things för cirkulär ekonomi. Metod: Studien använder sig utav en explorativ-kvalitativ forskningsmetod där primärdatan samlades genom semistrukturerade intervjuer. Datan transkriberades and kategoriserades med hjälp av Gioia-metoden, som sedan tillämpades till TOE-ramverket.  Resultat: Den här studien finner flera barriärer angående Blockchain of Things och Circular Economy, såsom brist på standardisering, brist på information och data, bristande kunskap, brist på regelverk och slutligen långsam förändrig av tankesätt hos beslutsfattare. Slutsats: Resultaten av studien pekar på större systemiska utmaningar av kunskap och standarder. Slutsatser som kan dras från detta är att industrin fortfarande befinner sig i tidig fas av digitaliseringen, vilket är anledningen till bristande insikt och kunskap om nya teknologier. Dessutom visar de identifierade utmaningar av brist på standarder, regleringar och tillvägagångssätt inom cirkulär ekonomi en brist på kunskap och förtroende för att kunna skapa konkurrenskraftiga, hållbara cirkulära aktiviteter.