Project Mariana: BIS and central banks of France, Singapore and Switzerland successfully test cross-border wholesale CBDCs

Updated 28 September 2023

  • Project Mariana tested the cross-border trading and settlement of wholesale CBDCs.
  • Successful trading and settlement of hypothetical euros, Singapore dollars and Swiss francs.
  • DeFi elements tested in the project, specifically automated market makers, could form the basis for a new generation of financial market infrastructures.

The Bank for International Settlements (BIS) and the central banks of France, Singapore and Switzerland have successfully concluded Project Mariana. The project tested the cross-border trading and settlement of wholesale central bank digital currencies (wCBDCs) between financial institutions, using new decentralised finance (DeFi) technology concepts on a public blockchain.

Project Mariana was developed jointly by three BIS Innovation Hub centres (the Swiss, Singapore and Eurosystem Hub Centres) together with Bank of France, Monetary Authority of Singapore and Swiss National Bank.

The project's proof of concept successfully tested the cross-border trading and settlement of hypothetical euro, Singapore dollar and Swiss franc wCBDCs between simulated financial institutions. The process relied on three elements:

  1. A common technical token standard provided by a public blockchain to facilitate exchange and interoperability between the different currencies.
  2. Bridges for the seamless transfer of wCBDCs between different networks.
  3. An Automated Market Maker (AMM), which is a specific type of decentralised exchange to trade and settle spot FX transactions automatically.
  • Final report (September 2023) 
  • Interim report (June 2023), published to elicit discussion and gather feedback on Project Mariana. It is superseded by the final report.

For Project Mariana, the AMM pooled the liquidity of the hypothetical euro, Singapore dollar and Swiss franc wCBDCs with innovative algorithms enabling spot FX transactions to be priced and executed automatically and settled immediately. These protocols could be used by the next generation of financial market infrastructures facilitating cross-border trading and settlement between financial institutions.

Project Mariana's architecture balances central banks' domestic need for oversight and autonomy with financial institutions' interest in efficiently holding, transferring, and settling wCBDC across borders. This is achieved through the use of a common token standard on a public blockchain which facilitates interoperability and seamless exchange of wCBDC across varied local payment and settlement systems maintained by participant central banks. As such, Mariana offers possible approaches to factoring an international dimension into current wCBDC design explorations.

As tokenisation and DeFi technologies are still nascent, further research and experimentation is needed. The BIS Innovation Hub and its global partners will continue exploring their benefits and challenges based on relevant use cases.

Project Mariana pioneers the use of novel technology for interbank foreign exchange markets. It successfully demonstrated that it is feasible to exchange wholesale CBDC across borders using novel concepts such as automated market makers. Bringing together a diverse team of software engineers, policy, and FX experts across three Innovation Hub centres and central banks was key to this success.

Cecilia Skingsley, Head of the BIS Innovation Hub

Project Mariana is purely experimental and does not indicate that any of the partner central banks intend to issue wCBDC or endorse DeFi or a particular technological solution. It is the Innovation Hub's first cross-centre project.