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.

Secure mobile apps, including end-to-end encrypted messaging apps such as Whats-App and Signal, are increasingly popular today. These apps require trust in a centralized key directory to automatically exchange the public keys used to secure user communication. This trust may be abused by malicious, subpoenaed, or compromised directories. A public key infrastructure (PKI) solution that requires less trust would increase the security of these commonly used apps.CONIKS is a recent PKI proposal that features transparent key directories which publish auditable digests of the public keys they present to queriers. By monitoring its key every time a new digest is published, a client can verify that its key is published correctly, reducing the need to trust the directory. CONIKS features improved security at the cost of unique auditing and monitoring requirements. In this thesis, we examine CONIKS' suitability as a PKI solution for secure mobile apps. We present a threat analysis of possible attacks on the CONIKS protocol and explore several important implications of CONIKS' system description, including recommendations for whistleblowing and key change policies. We also analyze mobile device usage data to estimate whether typical mobile device Internet connectivity is sufficient to fulfill CONIKS' monitoring requirement.

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>

This thesis proposes an implementation for a decentralized version of the Git version controlsystem. This is achieved using a simple distributed DAG ledger. The thesis analyzeshow the decentralization of Git affects security. Use and misuse cases are used to compareand evaluate conventional Git web services and a decentralized version of Git. Theproposed method for managing the state of the Git project is described as a voting systemwhere participants in a Git project vote on changes to be made. The security evaluationfound that the removal of privileged roles in the Git version control system, mitigated thepossibility of malicious maintainers taking over the project. However, with the introductionof the DAG ledger and the decentralization, the possibility of a malicious actor takingover the network using Sybil attack arises, which in turn could cause the same issues as amalicious maintainer.

The original FlexiChain and its descendants are a revolutionary distributed ledger technology (DLT) for cyber-physical systems (CPS) and their embedded systems (ES). FlexiChain, a DLT implementation, uses cryptography, distributed ledgers, peer-to-peer communications, scalable networks, and consensus. FlexiChain facilitates data structure agreements. This thesis offers a Block Directed Acyclic Graph (BDAG) architecture to link blocks to their forerunners to speed up validation. These data blocks are securely linked. This dissertation introduces Proof of Rapid Authentication, a novel consensus algorithm. This innovative method uses a distributed file to safely store a unique identifier (UID) based on node attributes to verify two blocks faster. This study also addresses CPS hardware security. A system of interconnected, user-unique identifiers allows each block's history to be monitored. This maintains each transaction and the validators who checked the block to ensure trustworthiness and honesty. We constructed a digital version that stays in sync with the distributed ledger as all nodes are linked by a NodeChain. The ledger is distributed without compromising node autonomy. Moreover, FlexiChain Layer 0 distributed ledger is also introduced and can connect and validate Layer 1 blockchains. This project produced a DAG-based blockchain integration platform with hardware security. The results illustrate a practical technique for creating a system depending on diverse applications' needs. This research's design and execution showed faster authentication, less cost, less complexity, greater scalability, higher interoperability, and reduced power consumption.

Consensus protocols are the core of modern blockchain systems, such as the Bitcoin, Ethereum, and Algorand networks. Thanks to these protocols, participants in a blockchain network can reach consensus on which blocks to add to a blockchain, to have a consistent chain of blocks in the whole network. Blocks are typically collections of transactions, e.g., transferring currency between participants, but can contain other data depending on the use case. Consensus protocols are difficult to design, test, and implement. Problems may only manifest in rare cases but can have disastrous consequences. Formal protocol models allow exhaustive analysis and formal verification. However, formal verification is only as good as the specification of the protocol. For example, specification properties could be vacuously true, or the specification may omit to mention liveness properties that are crucial for progress in a system implementation. This thesis describes the practical validation of a formal specification of Giskard, a consensus protocol used in the PlatON network. We translated key aspects of a formal model of Giskard in the Coq proof assistant to executable Python code, and integrated them into the Sawtooth blockchain framework. Then, we ran simulations of a blockchain network executing Giskard using Sawtooth, checking network node state properties of Giskard as well as its global safety properties. Automated clients from the Sawtooth network provided randomly generated transactions as input for the network. The implementation with the test results are available for reproducibility. Both consensus safety and liveness issues were found in the formal specification of Giskard during the simulations. Based on the previous informal English specification of Giskard, we propose a new formal specification which was validated to reach consensus on blocks in the simulated blockchain network and uphold the protocol’s crash and Byzantine failure tolerance to a certain degree. The improved formal model can serve as a new basis for verifying and implementing Giskard in the future. / Konsensusprotokoll utgör kärnan i moderna blockkedjesystem som Bitcoin-, Ethereum- och Algorandnätverken. Tack vare dessa protokoll kan deltagare i blockkedjenätverk nå konsensus om vilka block som ska läggas till, för att få en konsekvent blockkedja i hela nätverket. Block är vanligen samlingar av transaktioner, till exempel överföringar av valuta mellan deltagare, men kan också innehålla annan data beroende på användningsområdet. Konsensusprotokoll är svåra att designa, testa och implementera. Problem kanske bara visar sig i sällsynta fall, men kan ha katastrofala konsekvenser. Formella protokollmodeller tillåter uttömmande analys och formell verifiering. Men formell verifiering ger bara så goda resultat som protokollspecifikationen tillåter. Till exempel kan specfikationsegenskaper vara sanna innehållslöst eller så kan specifikationen underlåta att nämna framstegsegenskaper som är viktiga för att en systemimplementation inte ska låsa sig. Denna avhandling beskriver den praktiska valideringen av en formell specifikation av Giskard, ett konsensusprotokoll som används i PlatONnätverket. Vi översatte nyckelaspekter av en formell modell i bevisassistenten Coq till körbar Python-kod och integrerade koden i blockkedjeramverket Sawtooth. Sedan körde vi simuleringar av ett blockkedjenätverk som använder Giskard med hjälp av Sawtooth och undersökte Giskards tillståndsegenskaper för nätverksnoder och även dess globala säkerhetsegenskaper. Automatiserade klienter från Sawtooth-nätverket tillhandhöll slumpgenererade transaktioner som indata för nätverket. Implementeringen med testresultaten är tillgängliga för reproducerbarhet. Både säkerhets- och framstegsproblem hittades i den formella specifikationen av Giskard under simuleringarna. Baserat på en tidigare informell specifikation av Giskard på engelska föreslår vi en ny formell specifikation som validerades att nå konsensus på block i det simulerade blockkedjenätverket och att till en viss grad tolerera krascher och byzantinska fel. Den förbättrade formella modellen kan användas som en ny bas för att verifiera och implementera Giskard i framtiden.

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Organizations in the financial services industry are coming under increasing pressure. Regulatory compliance, operational inefficiencies, and the higher cost of capital are all forcing incumbents to adapt. As such, there are strong incentives for technological innovations that either reduce costs or generate new revenue. Distributed ledger technology (DLT), the foundation of bitcoin, is one of the latest innovations that appear to be the source of an imminent solution. An identified area with great potential for DLT is the post-trade market where market players, such as central securities depositories (CSDs), are heavily investing in pilot studies of how DLT may affect their business activities. In fact, the practical potential of adoption has been demonstrated by experiments and proof of concepts. However, while technological and regulatory aspects have been more frequently discussed in academia, the business dimension of the adoption of DLT within CSDs has received less attention. In this thesis, the business opportunities and challenges of the adoption of DLT within CSDs were explored, coupled with an analysis of the contextual factors affecting the rate of adoption. Further, this thesis compares the throughput performance between a centralized system and a private permissioned network. By performing a multiple-case study with a mixed-methodology approach, the researcher analyzed the literature, conducted a performance evaluation, and interviewed several industry experts. The conclusions suggest that the main business opportunities are the incorporation of digital assets and CSDs potential role as the gatekeeper of private networks. The main identified challenges related to adoption were interoperability, standardization, collaboration, scalability, defining applicable use cases, and governance and regulatory frameworks. Further, the performance evaluation suggests that the throughput performance of the centralized system outperforms the private permissioned network by an average of 6.5 times. The findings have both practical and academic implications. In academics, this thesis lays the foundation for further studies and provides new insights into the business dimensions of the adoption of DLT within CSDs. For practitioners, this thesis provides a basis for discussion and assessment of the entailed challenges related to the adoption of DLT within the post-trade market. / Organisationer inom finansbranschen utsätts för ökande press. Regelverksefterlevnad, operationell ineffektivitet och den högre kapitalkostnaden tvingar aktörer att anpassa sig. Som sådan finns det starka incitament för tekniska innovationer som antingen minskar kostnaderna eller genererar nya intäkter. Distribuerade liggare (DLT), grunden för bitcoin, är en av de senaste innovationerna som visar stor potential. Ett identifierat område med stor potential för DLT är post-trade-marknaden där marknadsaktörer, såsom centrala värdepappersförvarare (CSD), har investerat i pilotstudier av hur DLT kan påverka deras affärsverksamhet. Faktum är att den praktiska potentialen har demonstrerats genom experiment och bevis på koncept. Men även om tekniska och regulatoriska aspekter har diskuterats mer frekvent i den akademiska världen, har affärsdimensionen med införandet av DLT inom CSD:er fått mindre uppmärksamhet. I det här examensarbetet utforskades affärsmöjligheterna och utmaningarna med införandet av DLT inom CSDs, tillsammans med en analys av de marknadsmässiga faktorerna som påverkar spridningen av teknologin. Vidare jämför denna avhandling genomströmningsprestandan mellan ett centraliserat system och ett private permissioned nätverk. Genom att utföra en flerfallsstudie med en blandad metodologi analyserade forskaren litteraturen, genomförde en prestandautvärdering och intervjuade flera branschexperter. Slutsatserna tyder på att de huvudsakliga affärsmöjligheterna är integreringen av digitala tillgångar och CSD:s potentiella roll som gatekeeper för privata nätverk. De främsta identifierade utmaningarna i samband med införandet av DLT var interoperabilitet, standardisering, samarbete, skalbarhet, definition av tillämpliga användningsfall samt styrning och regelverk. Vidare antyder prestandautvärderingen att genomströmningsprestandan för det centraliserade systemet överträffar det private permissioned nätverket med i genomsnitt 6,5 gånger. Resultaten har både praktiska och akademiska implikationer. Inom akademin lägger denna avhandling grunden för fortsatta studier och ger nya insikter om affärsdimensionerna av införandet av DLT inom CSDs. För praktiker ger detta examensarbete ett underlag för diskussion och bedömning av de medförda utmaningarna relaterade till införandet av DLT inom post-trade-marknaden.

When the Internet was created it did not include any protocol for identifying the person behind the computer. Instead, the act of identification has primarily been established by trusting a third party. But, the rise of Distributed Ledger Technology has made it possible to authenticate a digital identity and build trust without the need of a third party. The Swedish Maritime Administration are currently validating a new maritime digital infrastructure for the maritime transportation industry. The goal is to reduce the number of accidents, fuel consumption and voyage costs. Involved actors has their identity stored in a central registry that relies on the trust of a third party. This thesis investigates how a conversion from the centralized identity registry to a decentralized identity registry affects the usability and the risk for compromised data integrity. This is done by implementing a Proof of Concept of a decentralized identity registry that replaces the current centralized registry, and comparing them. The decentralized Proof of Concept’s risk for compromised data integrity is 95.1% less compared with the centralized registry, but this comes with a loss of 53% in efficiency.

With the invention of the cryptocurrency Bitcoin in 2009, the world's first blockchain application was developed. While academic research gradually begins to investigate cryptocurrencies more closely and attempt to understand their functioning, technology is rapidly evolving and ecosystems grow exponentially. The research is still scattered and chaotic and has not produced common guidelines. Therefore, the question remains: how sustainable cryptocurrencies and their digital ecosystems are.Only a few models and frameworks take a holistic view on digital sustainability. Only two frameworks were identified that take distributed ledger technologies (blockchain) or cryptocurrencies into consideration: the three governance strategies for digital sustainability of Linkov et al. (2018) and 10 basic conditions of sustainable digital artifacts according to Stuermer, Abu-Tayeh and Myrach (2016). These two frameworks were combined into a new integrated sustainability framework for cryptocurrencies. The developed integrated sustainability framework consists of four dimensions and 12 categories.Existing secondary data, self-conducted social media interviews and practical insights gained through an ASIC mining experiment were used to fill the framework with sufficient data. It confirms Bitcoin's sustainability problems in energy consumption and scalability, highlights Ethereum's great potential as a blockchain platform and explains the higher scalability and faster payment of Ripple and IOTA.While 2017 marked the temporary peak of the cryptocurrency hype, 2018 was a transformative year in which the leading cryptocurrencies were increasingly occupying more specialised niches.