WhatsApp is updating its messenger app so that every text and voice call on one of the world’s most popular apps will be protected with strong encryption – potentially putting millions more conversations outside the purview of authorities.

The development at the messenger company, which is owned by Facebook, is striking given Silicon Valley’s recent staredown with authorities over user data privacy.

The FBI dropped a court battle with Apple over its iPhone encryption, and Brazilian police recently arrested a Facebook executive because WhatsApp couldn’t provide messages sent by a criminal suspect.

None of that appears to have deterred WhatsApp founder Jan Koum, who grew up in Soviet-era Ukraine amid surveillance fears and has said that he often heard his mother say things like, “This isn’t a telephone conversation.”

“The desire to protect people’s private communication is one of the core beliefs we have at WhatsApp, and for me, it’s personal,” Koum wrote in a blog post published Tuesday. “I grew up in the USSR during communist rule and the fact that people couldn’t speak freely is one of the reasons my family moved to the United States.”

The Guardian reported on WhatsApp’s plans in March.

All of WhatsApp’s 1 billion users, when running the latest version of the app on iPhone, a Google Android device, Nokia or Blackberry, will send and receive messages, attachments and voice calls that engineers say can only be deciphered by the intended recipient, said Moxie Marlinspike, an encrypted messaging developer at Open Whisper Systems, whose technology forms the backbone of WhatsApp’s encryption.

This means WhatsApp shouldn’t be able to facilitate a wiretap of the contents of users’ messages, even if faced with a court order. It’s unclear if the company will be able to help authorities intercept data on when they use WhatsApp or with whom they communicate.

Additionally, WhatsApp will take the unusual step for a consumer app of notifying users if messages are encrypted, Marlinspike said.

If several users are trading texts in a group message and one of the users is running an older version of the app that doesn’t support encrypted group messages, the others will be able to tell which person is causing the session to remain unencrypted.

This is a departure from other mainstream technology companies, which have typically not highlighted security features for fear of provoking authorities or irritating disinterested consumers.

WhatsApp appears to be betting that three years after Edward Snowden’s revelations rekindled a global debate over digital surveillance, consumers do care about data security as a deciding issue in which apps they will use.

Telegram, a Berlin-based messaging service that has grown dramatically since 2013, has made similar bets as it offers privacy features. Meantime, Google and Snapchat both are exploring their own encrypted messaging services.

WhatsApp and Facebook representatives did not immediately return requests for comment.

WhatsApp began adding strong encryption as a default for some messages in late 2014, but it only worked for users on certain phones or in certain situations. Users also did not know if the encryption was or was not engaged, making the technology undependable for those most concerned about digital privacy, such as human rights works, dissidents and whistleblowers.

WhatsApp has spent 18 months discreetly expanding encryption throughout its service.

Marlinspike is a San Francisco-based developer who runs Signal, an encrypted messaging app similar to WhatsApp and popular among privacy advocates. He described the challenge as stark, being recruited to help WhatsApp’s engineering team add complicated encryption features to a service used by one billion people.

The programmer said he plans to help other apps add his encryption in the future, though he declined to state who he may or may not be working with. “We’re going to keep doing stuff like this,” he said.

There is also some irony in WhatsApp’s move given the current political debate.

Marlinspike developed his encryption tools with a grant from Radio Free Asia, which is funded by Congress.

On Monday, Senator Richard Burr, chairman of the Senate intelligence committee, said he planned to soon unveil legislation that would regulate encrypted communications.

In the blog post, Whatsapp acknowledged the recent controversy around encryption but downplayed any political implications of its most recent update. Rather, it said it was trying to protect consumers from hackers and “oppressive regimes.”

“All you need to know is that end-to-end encrypted messages can only be read by the recipients you intend,” the company said.