Recent years have seen an increasing interest in stablecoins from major corporate and governmental parties. The European Central Bank is investigating the possibility of introducing its own Central Bank Digital Currency. The desired features of such a currency are under discussion. One such feature is offline spending: the ability to use the currency without an internet connection, like cash. This thesis describes a token-based transaction prototype and its implementation on the Kotlin-IPv8 protocol stack. The prototype allows funds to be spent in an offline setting and provides retroactive fraud detection. The prototype is not intended for deployment but instead serves as a trial for building digital currencies on Kotlin-IPv8. The included performance analysis demonstrates that various facets of Kotlin-IPv8 perform suboptimally, of which most notably its UDP data throughput.

Switching energy suppliers can be a time consuming process and the manner in which permissions regarding consumer data are stored lacks transparency. To overcome these issues, a solution was proposed in the form of a mandate register. Said register keeps track of which consumer gave what permission, regarding energy data, to whom. In this project a prototype of such a register was built. The register is required to be designed in such a way that it is expandable and secure. From these characteristics, the conclusion was drawn that a permissioned blockchain network was the most suitable option for storing mandates in a decentralised and immutable fashion. The most fitting consensus algorithm for the blockchain network was determined to be the Raft algorithm. For implementation of the blockchain network, a widely-documented and advanced framework called Hyperledger Fabric was used, which was be configured to use Raft. A network in Hyperledger Fabric is a set of organisations of which subsets can form channels together. Each organisation consists of multiple peer nodes, each with a corresponding ledger, database and smart contracts. The mandate register network consists of two channels, the first containing seven organisations, with two peer nodes per organisation. Apart from these seven organisations, the network contains seven orderers, which work in the second channel and which are responsible for managing transactions made by an application. On top of the network, an application was built that connects to the network and functions as a simple web server. The web server allows consumers to submit their mandates as input to the network and query mandates from the network. Performance evaluation of the network shows that it requires much optimisation before being ready for deployment in the real world. Apart from optimisation, there are various tasks related to security, authentication, deployment, and the GDPR which have to be completed before the register can be used in production.