The government of Buenos Aires has included zero-knowledge proofs in its app to access city services.
ZK proofs allow users to prove something is true about a set of data without revealing that data, such as that they are a certain age without giving their date of birth.
The technology is being tested in other jurisdictions, including Uruguay.
The city of Buenos Aires has launched a digital identity service designed to strengthen residents’ privacy using zero-knowledge proofs, a type of cryptography that dates back a long time, but often strengthens cryptocurrencies.
The QuarkID service is integrated into miBA, the city’s seven-year-old app for access to municipal services and documents. The idea, in short, is to give 3.6 million porteños – residents of Buenos Aires – more control over their personal data. ZK proofs allow users to prove that a document has indeed been authenticated by the government, without revealing information that is not relevant to the task at hand.
For example, residents can open the app on their phone to confirm that they are over a certain age (for the purpose of purchasing alcohol, for example) without showing their address or even their full date of birth.
“The decision from the beginning was to create a self-sovereign identity system so that citizens can have privacy and security over the documents they take ownership of,” Diego Fernandez, Minister of Innovation and Digital Transformation of Buenos Aires, told CoinDesk .
Zero-knowledge proofs don’t require a blockchain to work, but QuarkID uses one: the Ethereum layer-2 network ZKsync Era. According to QuarkID’s website, the blockchain serves as a “security anchor,” meaning it’s there to prove that a piece of data existed in a certain form at a certain time. “Relying solely on the issue date embedded in the credentials can be problematic as a malicious publisher can backdate documents,” Fernandez said.
More than 60 different types of documents — including birth certificates, gross receipts tax certificates and vaccination records — can be uploaded to the app, and more will be made available in the coming months, the city said.
So no third party, not even the municipality of Buenos Aires, has any control over these documents According to the press release, porteños do not have to worry about their information being hacked and released into the wild. The risk of identity theft is thus greatly reduced. And neither the government nor QuarkID can track the use of these credentials, the release said.
“There are no costs for users,” says Fernandez. “In fact, it offers vastly lower costs to the government than traditional methods.”
The experiment extends beyond Buenos Aires. Pilots are in the works in various Argentine regions, with Jujuy and Tucumán rolling out the technology on a larger scale. Luján de Cuyo, a small town in the Mendoza region, is also experimenting at the municipal level.
“The city of Buenos Aires and the national government have an IP sharing agreement, so any technology developed and implemented in the capital can be shared with the national government,” Fernandez said. “We plan to implement and test this in Buenos Aires, and we hope we can then scale nationally.”
Experiments are taking place in other Latin American countries, including Uruguay, Fernandez said.