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.

Blockchain is a Distributed Ledger Technology that was popularized after the release of Bitcoin in 2009 as it was the first popular blockchain application. It is a technology for maintaining a digital and public ledger that is decentralized, which means that no single authority controls nor owns the public ledger. The ledger is formed by a chain of data structures, called blocks, that contain information. This ledger is shared publicly in a computer network where each node is called a peer. The problem that arises is how to make sure that every peer has the same ledger. This is solved with consensus mechanisms which are a set of rules that every peer must follow. Consensus mechanisms secure the ledger by ensuring that the majority of peers can reach agreement on the same ledger and that the malicious minority of peers cannot influence the majority agreement. There are many different consensus mechanisms. A problem with consensus mechanisms is that they have to make a trade-off between low energy consumption and high security. The purpose of this report is to explore and investigate the relationship between energy consumption and security in consensus mechanisms. The goal is to perform a comparative study of consensus mechanisms from an energy consumption and security perspective. The consensus mechanisms that are compared are Proof of Work, Proof of Stake and Delegated Proof of Stake. The methodology used is literature study and comparative study by using existing work and data from applications based on those consensus mechanisms. The results conclude that Proof of Work balances the trade-off by having high energy-consumption and high security, meanwhile Proof of Stake and Delegated Proof of Stake balance it by having low energy consumption but lower security level. In the analysis, a new factor arose, decentralization. The new insight in consensus mechanisms is that decentralization and security is threatened by an inevitable centralization where the ledger is controlled by few peers. / Blockchain är en så kallad distribuerad huvudbok teknologi som fick ett stort genombrott med den populära blockchain applikationen Bitcoin i 2009. Teknologin möjliggör upprätthållandet av en digital och offentlig huvudbok som är decentraliserad, vilket betyder att ingen ensam person eller organisation äger och kontrollerar den offentliga huvudboken. Huvudboken i blockchain är uppbyggt som en kedja av block, dessa block är datastrukturer som innehåller information. Huvudboken distribueras i ett nätverk av datorer som kallas för noder, dessa noder ägs av en eller flera personer. Problemet är att alla noderna i nätverket måste ha identiska huvudbok. Detta problem löses med en uppsättning av regler som noderna måste följa, denna uppsättning kallas för konsensus mekanism. Konsensus mekanismer säkrar huvudboken genom att möjliggöra en överenskommelse bland majoriteten av noderna om huvudbokens innehåll, och ser till att oärliga noder inte kan påverka majoritetens överenskommelse. Det finns flera olika konsensus mekanismer. Ett problem med konsensus mekanismer är att de är tvungna att göra en avvägning mellan låg energianvändning och hög säkerhet. Syftet med denna rapport är att undersöka och utreda relationen mellan energianvändning och säkerhet i konsensus mekanismer. Målet är att utföra en komparativ analys av konsensus mekanismer utifrån energianvändning och säkerhet. Konsensus mekanismerna som jämförs är Proof of Work, Proof of Stake och Delegated Proof of Stake. Metodologin som används är litteraturstudier och komparativ analys med hjälp av existerande metoder och data från applikationer som använder konsensus mekanismerna. Resultatet visar att Proof of Work väljer hög säkerhet på bekostnad av hög energianvändning, medan Proof of Stake och Delegated Proof of Stake väljer låg energianvändning men på bekostnad av lägre säkerhet. Analysen ger en ny inblick som visar att centralisering är en oundviklig faktor som hotar säkerheten.

<p dir="ltr">Amidst the rising popularity of digital marketplaces, addressing issues such as non-<br>payment/non-delivery crimes, centralization risks, hacking threats, and the complexity of<br>ownership transfers has become imperative. Many existing studies exploring blockchain<br>technology in digital marketplaces and asset management merely touch upon various application scenarios without establishing a unified platform that ensures trustworthiness and<br>efficiency across the product life cycle. In this thesis, we focus on designing a reliable and efficient e-commerce model to trade various assets. To enhance customer engagement through<br>consensus, we utilize the XGBoost algorithm to identify loyal nodes from the platform entities pool. Alongside appointed nodes, these loyal nodes actively participate in the consensus<br>process. The consensus algorithm guarantees that all involved nodes reach an agreement on<br>the blockchain’s current state. We introduce a novel consensus mechanism named Modified-<br>Practical Byzantine Fault Tolerance (M-PBFT), derived from the Practical Byzantine Fault<br>Tolerance (PBFT) protocol to minimize communication overhead and improve overall efficiency. The modifications primarily target the leader election process and the communication<br>protocols between leader and follower nodes within the PBFT consensus framework.</p><p dir="ltr"><br>In the domain of tangible assets, our primary objective is to elevate trust among various<br>stakeholders and bolster the reputation of sellers. As a result, we aim to validate secondhand<br>products and their descriptions provided by the sellers before the secondhand products are<br>exchanged. This validation process also holds various entities accountable for their actions.<br>We employ validators based on their location and qualifications to validate the products’<br>descriptions and generate validation certificates for the products, which are then securely<br>recorded on the blockchain. To incentivize the participation of validator nodes and up-<br>hold honest validation of product quality, we introduce an incentive mechanism leveraging<br>Stackelberg game theory.</p><p dir="ltr"><br>On the other hand, for optimizing intangible assets management, we employ Non-Fungible<br>Tokens (NFT) technology to tokenize these assets. This approach enhances traceability of<br>ownership, transactions, and historical data, while also automating processes like dividend<br>distributions, royalty payments, and ownership transfers through smart contracts. Initially,<br>sellers mint NFTs and utilize the InterPlanetary File System (IPFS) to store the files related<br>to NFTs, NFT metadata, or both since IPFS provides resilience and decentralized storage solutions to our network. The data stored in IPFS is encrypted for security purposes.<br>Further, to aid sellers in pricing their NFTs efficiently, we employ the Stackelberg mechanism. Furthermore, to achieve finer access control in NFTs containing sensitive data and<br>increase sellers’ profits, we propose a Popularity-based Adaptive NFT Management Scheme<br>(PANMS) utilizing Reinforcement Learning (RL). To facilitate prompt and effective asset<br>sales, we design a smart contract-powered auction mechanism.</p><p dir="ltr"><br>Also, to enhance data recording and event response efficiency, we introduce a weighted<br>L-H index algorithm and transaction prioritization features in the network. The weighted<br>L-H index algorithm determines efficient nodes to broadcast transactions. Transaction prior-<br>itization prioritizes certain transactions such as payments, verdicts during conflicts between<br>sellers and validators, and validation reports to improve the efficiency of the platform. Simulation experiments are conducted to demonstrate the accuracy and efficiency of our proposed<br>schemes.<br></p>