Instead of hackers merely looking at your financial data, what if they could add a million dollars to your debt?

What about $10 million?

It’s possible, Guardtime’s Mike Gault told Quartz. And not just with financial data, but with health-care records, military information, and other sensitive data. Guardtime is helping Estonia move its citizens’ health records to a database, based on blockchain technology, that nobody can mess with.

While financial institutions rave about the potential for blockchain—the technology that powers bitcoin—as a way to revolutionize the financial world, it can also help keep private data secure. A blockchain is essentially a digital ledger that, thanks to some computational tricks, records every change made to it indelibly.

This means it can act as a database for health data. Whenever someone’s health records are accessed, that “event” is recorded on the blockchain, alongside what information was changed or added, Gault said. That way, the information remains both secure and tamper-proof; nobody can change it without leaving traces. Eventually, there will be a dashboard for the public to see their own health records and any changes made to them.

Estonia, a country that has over 1,000 digital services, is a digitally advanced society. For several years already, people have been able to access their medical records and other data online, see who else has looked at them, and grant permission to certain people (such as medical specialists) to see them. But a blockchain will make it impossible for hackers to hide their tracks if they access or change data during an attack, and provide real-time alerts if a data breach occurs.

With traditional protection systems like firewalls, an attack may go undetected for a long time. When Target was hacked in 2013, it took the company a month to find out. The US National Security Agency still has not figured out what information Edward Snowden accessed; blockchain-based security could have made his theft of data impossible without detection.

Maintaining the integrity of important data—making sure that it can’t be altered—is a key concern for governments. Some of the US’s top intelligence officials have spoken up recently about the worry that in future, hackers won’t just steal government data but manipulate it to sow distrust and cripple decision-making.

Estonia will be the first country to use blockchain this way, according to a press release issued today (March 3). Other governments are slowly warming up to blockchain technology. In Jan. 2016, a report from the UK Government Office of Science recommended the government start testing distributed-ledger technology (another name for it). Other countries, like Japan and Russia, are learning more about it too.