After the release of Bitcoin in 2008 many advances have been made in the crypto space. The feature-set, scalability, transaction cost, and efficiency have all improved. Yet, as the development continued, the goal of Bitcoin or any other cryptocurrency as a digital payment form started to take a backseat to their utility as a store of value and investment vehicle. Additionally, cryptocurrencies are missing the crutial features of scalability in transactions per second and basic price stability. This calls into question whether fully decentralized currencies can ever serve as a global payment system.

Meanwhile, the world of payments outside the crypto-sphere is going through a transformation. With the use of physical money declining in favor of privately banked money, payment systems are going digital. Yet, banks are being found unreliable, unavailable to many people across the world, and unable to match the convenience and feature set of new payment providers. With decentralized cryptocurrencies not sufficing as payment solutions, centrally controlled currencies like Tether and Diem (previously Libra) are trying to fill the exact hole in the market left by banks. Consequently, the global digital payment system may eventually belong to the first bidder, be they decentralized, run by governments, or by private, profit driven corporations.

We present EuroToken, a design for a CBDC that is focused on solving the open issues in cryptocurrencies from the perspective of a trustworthy central bank. By centralising some infrastructure required to run a cryptographically secure currency, we achieve a network that can scale to arbitrary size, handle offline transactions, and remain price-stable and guaranteed in value by the Central Bank.

The EuroToken system is a Peer-to-Peer blockchain system that stores every wallets' history on the users personal device. This allows basic transactions without an online connection. Double-spend prevention is handled by a set of centralised nodes that periodically verify the transactions of a given user and condenses their chain into a single "checkpoint" block for scalability. In order to create price stability, we attach EuroToken to the IBAN system and enable a 1:1 exchange in either direction.

We present a working implementation of EuroToken including a wallet and an IBAN / EuroToken exchange. We also show how our system can grow to an arbitrarily large scale without sacrificing efficiency.