Last week Banco Central do Brasil formally announced a delay in its DREX central bank digital currency (CBDC) initiative because it still needs to do more work exploring privacy solutions. In the meantime it plans to launch phase 2 which will broaden the range of use cases, with a call for suggestions expected in the third quarter. Testing of additional applications will happen during the first half of 2025. With this expansion, the governance of the CBDC platform will need to evolve. The Securities and Exchange Commission (CVM) will likely join the governance structure following its observer role during phase 1.
As context, DREX is a wholesale CBDC solution with the digital real used for interbank settlement. The retail facing digital currency is the form of tokenized deposits from commercial banks. The project focuses on enabling programmability and using blockchain and tokenization for financial transactions such as investments.
During the first phase, the DREX platform had only three assets and a single application. The assets were the wholesale CBDC, tokenized deposits and digital treasury bonds (Federal public bonds). Hence, smart contracts written by the central bank enabled their issuance, transfer and settlement. The second stage will become much more interesting with a broader range of use cases. Since it will involve securities, the CVM needs to be involved in the governance.
Maturity of privacy solutions
The formal announcement of the delay by the central bank stated that “privacy solutions tested up to the present stage of the Pilot have not presented the necessary maturity to guarantee compliance with all legal requirements related to preserving citizens’ privacy, despite having evolved over time.”
However, central bank project staff emphasized the “up to the present stage” aspect. It is still a work in progress.
They planned to evaluate privacy functionality through May, and the work wasn’t yet completed to their satisfaction. They noted that their use case involving two currencies and the Federal bond was more complex than most, so they ran into issues. In some cases, the issues weren’t with the basic transactions, such as transferring money. Challenges arose in testing delivery versus payment.
The three privacy solutions tested
The DREX platform uses a permissioned version of Ethereum’s Hyperledger Besu, with multiple parties hosting the blockchain’s nodes. Given blockchains are inherently transparent, there’s a need for a privacy solution in order to comply with bank privacy legislation.
So far the central bank has tested three privacy solutions: Anonymous Zether, Ernst and Young’s Starlight and Parfin’s Rayls. The first one didn’t work for its purposes, but EY and Parfin adapted their solutions. They only just received the latest EY iteration and the updated Parfin solution requires extensive testing. Hence, the conclusion that the status of testing sounds more like a work in progress than ‘it doesn’t work’. That said, the solutions being tested are pretty bleeding edge, as opposed to having long track records in use.
Additionally, Microsoft, one of the pilot participants, proposed its solution ZKP Nova, which the central bank is starting to explore.
Technically Anonymous Zether, Starlight and ZKP Nova involve zero knowledge proofs, whereas Rayls is a blockchain interoperability solution that supports integrating private blockchains using private bridges. Accenture is a backer of Rayls developer Parfin, which counts Brazil’s stock exchange as a client and is partnering with Santander for the digital Real pilots.
One advantage of the delay is that the privacy solutions can be tested in a more complex environment with expanded use cases.
DREX for open banking
Meanwhile, in 2020 the central bank launched the Pix instant payment solution which has been a resounding success. DREX is not positioned as a pure payment solution. Instead it is for programmable payments and for open banking-like functionality. Ultimately the goal is to enable financial inclusion by making it cheaper to access credit or make investments.
