FOR MOST OF the past six weeks, the biggest story out of Silicon Valley was Apple’s battle with the FBI over a federal order to unlock the iPhone of a mass shooter. The company’s refusal touched off a searing debate over privacy and security in the digital age. But this morning, at a small office in Mountain View, California, three guys made the scope of that enormous debate look kinda small.

Mountain View is home to WhatsApp, an online messaging service now owned by tech giant Facebook, that has grown into one of the world’s most important applications. More than a billion people trade messages, make phone calls, send photos, and swap videos using the service. This means that only Facebook itself runs a larger self-contained communications network. And today, the enigmatic founders of WhatsApp, Brian Acton and Jan Koum, together with a high-minded coder and cryptographer who goes by the pseudonym Moxie Marlinspike, revealed that the company has added end-to-end encryption to every form of communication on its service.

This means that if any group of people uses the latest version of WhatsApp—whether that group spans two people or ten—the service will encrypt all messages, phone calls, photos, and videos moving among them. And that’s true on any phone that runs the app, from iPhones to Android phones to Windows phones to old school Nokia flip phones. With end-to-end encryption in place, not even WhatsApp’s employees can read the data that’s sent across its network. In other words, WhatsApp has no way of complying with a court order demanding access to the content of any message, phone call, photo, or video traveling through its service. Like Apple, WhatsApp is, in practice, stonewalling the federal government, but it’s doing so on a larger front—one that spans roughly a billion devices.

“Building secure products actually makes for a safer world, (though) many people in law enforcement may not agree with that,” says Acton, who was employee number forty-four at Internet giant Yahoo before co-founding WhatsApp in 2009 alongside Koum, one of his old Yahoo colleagues. With encryption, Acton explains, anyone can conduct business or talk to a doctor without worrying about eavesdroppers. With encryption, he says, you can even be a whistleblower—and not worry.