Two-tier distribution model of retail CBDC

Projet Aurum studies the benefits and challenges of tiered architectures for the distribution of retail CBDC through commercial banks and payment service providers. This project will investigate two architectural models: hybrid CBDC and private CBDC-backed e-money.

The Aurum project will explore a series of complex design questions:

Flexible architecture

  • Is it possible to have a flexible two-tier architecture which supports both hybrid central bank digital currency (CBDC) and CBDC-backed e-money?
  • Can interaction between the two levels of ledgers be minimised through suitable design?

Over-issuance prevention

  • Can technology help to ensure an issuer follows the rules and protocol?
  • Can we be certain that the two levels of ledgers are always congruent?
  • Can over-issuance of e-money be prevented with suitable design of transaction structure?
  • Can the same structure allow us to detect who has cheated?


  • Can the design tell who the issuer is for a given amount of e-money held by a user?
  • Can the design tell which CBDC backing asset should be released when e-money is redeemed?
  • Can the design tell which CBDC transaction is used to back a certain amount of e-money in order to honour a claim when the issuer is insolvent?