Content delivery networks (CDNs) depend on distributed cache servers to reduce the content delivery distance and latency to end users. Nevertheless, a CDN's cache footprint is greatly limited by the high cost in deploying and maintaining large- scale cache servers. To break the limit, CDN providers adopt a new content caching strategy that allows end users to share their storage/bandwidth resources with each other. Two core questions need to answer in this CDN strategy: (1) how to incentivize end users to contribute their resources? and (2) how to facilitate transparent, secure content exchange among end users? We propose a new CDN solution, called SmartSharing, where users contribute their Over-the-top (OTT) devices as mini cache servers. With SmartSharing, an OTT device can share the content the OTT owner is downloading and in addition can cache content for neighboring OTT devices in the same area. To incentivize end users to contribute their resources, SmartSharing uses game theory and the Expectation- Maximization (EM) algorithm to determine content delivery schedule and the pricing scheme. To facilitate content trading among end users, SmartSharing uses smart contracts in Ethereum to create a transparent and safe transaction platform. We evaluate SmartSharing with real-world trace driven simulation as well as smart con- tract prototype in Ethereum using content meta-data and the derived pricing scheme. By disclosing the internal dynamics in content delivery schedule and pricing scheme and analyzing the overhead in content trading, we show that SmartSharing is an effective new CDN solution that benefi ts content providers, CDN, and end users. / Graduate

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The main purpose of a vehicle information system using blockchain is to create a transparent and reliable information system which will help consumers buy a vehicle; it is a vehicle information system. The blockchain system will create a time sequence chain of events database for each vehicle from the original sale. It will include insurance, vehicle repair, and vehicle resale. This project is mainly divided into three parts. Part one is used by the administration who will create the blockchain and will give authentication to a different organization to create the blockchain. Part two will be used by the Organization to create a block in the blockchain. Part three will be used by customers who want to get information about the vehicle.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / The demand for agricultural products for export is increasing every year. Thus, there is a need for a traceable and more communicative agricultural supply chain among its stakeholders. In addition, the increase in controls, verifications and communications in each SC agent makes agility and chain difficult, generating distrust among those involved. To overcome this issue, we consider Blockchain. Blockchain is a disruptive technology to decentralize data with this state-of-the-art technology, we develop a model that solves the traceability problem of the agricultural product. The model also improves transparency and security within the SC, increasing trust between the suppliers, collaborators and consumers.

This thesis seeks to shed further light on how blockchain technology has fostered increases in efficiency at an overall level looking specifically at the Ethereum network, and a continued analysis of its evolving state. A network at the forefront of blockchain technology and smart contract utilization. Firstly, we introduce blockchain technology itself and the various facets of the technology, including consensus protocols, smart contracts and smart contract applications. Subsequently, we further analyse and showcase how blockchain technology has developed in efficiency over its maturation recently. Through the employment of various econometric models and strong discussion promotes insights to the key metrics of the Ethereum network. Finally, we explore whether we are able to note these changes over time and look to the future of blockchain technology. Not only to shed light on how this evolving state will continue to cultivate but also detail the other necessary advances needed to continue this growth.

Smart contracts are digital agreements stored and executed on a blockchain. With smart contracts, multiple parties can enter into an agreement whose correct execution is guaranteed by the underlying blockchain. However, there is no inherent way for smart contracts to access data APIs external to the blockchain they reside on, which is needed in order to expand their usefulness. This thesis investigates two approaches of feeding data to a smart contract on the Ethereum blockchain, with regard to the performance metrics gas cost, block delay, and network latency. The investigation is set in the context of train travel where the time of arrival of a train at its destination is retrieved to the smart contract. Receiving and aggregating submissions from varying numbers of passengers is compared to retrieving this data from the dedicated open API provided by Trafikverket using the Chainlink framework. Through experiments, involving issuing transactions and monitoring them, it was found that in the case of passenger submissions with aggregation the gas costs had a linear relationship to the amount of passengers submitting data. Compared to lower amounts, the block delay for passenger submissions started seeing an increase at 100 to 300 submissions whereas it was more or less constant for aggregations. Furthermore, there was no noticeable trend for increase in network delay with increase of submissions. Conclusively, with regard to all performance metrics, it was found that in all cases involving more than five passengers it was cheaper to use Chainlink to fetch data from Trafikverket.

The emergence of blockchain technology and increasing penetration of distributed energy resources (DERs) have created a new opportunity for peer-to-peer (P2P) energy trading. However, challenges arise in such transactive markets to ensure individual rationality, incentive compatibility, budget balance, and economic efficiency during the trading process. This thesis creates an hour-ahead P2P energy trading network based on the Hyperledger Fabric blockchain and explores a comparative analysis of different auction mechanisms that form the basis of smart contracts. Considered auction mechanisms are discriminatory and uniform k-Double Auction with different k values. This thesis also investigates effects of four consumer and prosumer bidding strategies: random, preference factor, price-only game-theoretic approach, and supply-demand game-theoretic approach. A custom simulation framework that models the behavior of the transactive market is developed. Case studies of a 100-home microgrid at various photovoltaic (PV) penetration levels are presented using typical residential load and PV generation profiles in the metropolitan Washington, D.C. area. Results indicate that regardless of PV penetration levels and employed bidding strategies, discriminatory k-DA can outperform uniform k-DA. Despite so, discriminatory k-DA is more sensitive to market conditions than uniform k-DA. Additionally, results show that the price-only game-theoretic bidding strategy leads to near-ideal economic efficiencies regardless of auction mechanisms and PV penetration levels. / MS

A smart contract is a recently emerging technology which enables agreement to be automatable by computers and enforceable by legal enforcement or tamper-proof execution of code. A majority of smart contracts are run on the blockchain which enables smart contract transactions without a central authority. Smart contract implementation contains several challenges which makes implementation more difficult. The problem is that organisations struggle to implement smart contracts due to the absence of documentation, standardisation, and guidelines making it difficult to know how a smart contract should be implemented. Additionally, it is unclear what capabilities and tools are required for smart contract implementation. Therefore, it is challenging for organisations to assess their own competence of smart contract implementation. This thesis aims to develop a Smart Contract Maturity Model (SCMM). The purpose of the model is to clarify the functionalities and capabilities required to implement a smart contract while also offering organisations the ability to assess the smart contract implementation competency. This improves the adoption of smart contracts. Through the help of the design science framework, the SCMM emerged from the thesis. Applying design science included explicating the problem, defining requirements, designing and developing the artefact, demonstrating and evaluating the artefact. A literature survey was used to explicate the problem and to define requirements for the maturity model. Furthermore, a case study including interviews were used to refine the requirements and to demonstrate and evaluate the SCMM. The SCMM includes maturity levels, generic goals and practices, specific goals, key processing areas and practices, tools, glossaries and smart contract examples. Inspired by the Capability Maturity model Model Integration for Development (CMMI-DEV), the maturity levels of the SCMM consisted of initial, foundation, managed, defined, quantitatively managed and optimising. The identified key processing areas were stakeholder capabilities, resources and tools, platform, contract implementation, standards, laws and terminology and security. Although there were several limitations, the SCMM contributed to the field of smart contracts by closing the gap of previous research and improving the adoption of smart contracts.

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.