Since 2016, the social behemoth now often called Meta has been working to deploy end-to-end encryption in its communication apps. CEO Mark Zuckerberg even promised in 2019 that the information privateness safety would roll out by default throughout the entire firm’s chat apps. In observe, although, it was a wildly bold objective fraught with technical and political challenges, and Meta has solely been in a position to transfer toward it in gradual, incremental steps. But this week the corporate is lastly beginning its full rollout.

“It’s been a wild ride,” says Jon Millican, a software engineer within Meta’s messenger privacy team. “I suspect this is the first time that something’s been end-to-end encrypted with all of the constraints that we’re working with. It’s not just that we’re migrating people’s data, but it’s actually that we’re having to fundamentally change a bunch of the assumptions that they work with when they’re using the product.”

Meta has had to stake out a position as a committed proponent of end-to-end encryption amid pressure from law enforcement and victim advocacy groups that the privacy feature—which makes data unintelligible everywhere except on the devices of the sender and recipient—limits necessary oversight and impedes crucial police investigations. Meanwhile, the company has spent the past four years, not to mention the better part of a decade, developing the technology to retrofit two massive communication platforms—Messenger and Instagram chat—such that they could still offer the features and general experience users expect under the technical constraints and usability challenges of end-to-end encryption.

“I understand that many people don’t think Facebook can or would even want to build this kind of privacy-focused platform—because frankly, we don’t currently have a strong reputation for building privacy-protective services, and we’ve historically focused on tools for more open sharing,” Zuckerberg memorably wrote in his 2019 treatise. But he added that there was a transparent want from customers to have entry to non-public and safe encrypted communication companies. “This is the future I hope we will help bring about,” he wrote.

Meta says that it’s going to take a while for the rollout of full default end-to-end encryption to achieve all Messenger and Instagram chat customers, and the characteristic remains to be solely launching for direct messages between two accounts. End-to-end encryption for group chats will proceed to be opt-in for now. But these ultimate delays must do with regularly changing billions of accounts to run the cryptography and encrypted storage schemes that underly the trouble. And whereas the infrastructure is new and needed to be painstakingly tailor-made to Meta’s companies, the corporate says it constructed the system on the Signal Protocol and thoroughly vetted the implementation both internally and with independent experts. In the lead-up to this announcement, the company did a final round of outreach to privacy groups and cryptographers to show them the documentation and have them test the feature.

“It looks just like Messenger, except that under the hood it has really strong encryption,” says Matt Green, a Johns Hopkins cryptographer who previewed the launch a number of weeks in the past. “Getting things to work on the web seems like it was the hard part, but they pulled it off.”