Whatsapp locked down its popular messaging service Tuesday, using end-to-end encryption to protect user communications against prying eyes. 

“I do think this is the largest deployment of end-to-end encryption ever,” Open Whisper Systems CTO Moxie Marlinspike told Wired. His organization, a nonprofit focused on user security, makes the Textsecure open-source privacy software used by Whatsapp for its large-scale cryptographic anti-snooping measure. 

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End-to-end encryption refers to an especially secure measure in which messages are not decrypted until they land on the recipient’s device. A far more common approach would be to encrypt messages when they travel between the user’s device and the text messaging app’s server, which amounts to just half of the message’s total journey. iMessage is reportedly the only other service that uses end-to-end encryption, and Apple’s approach seemingly becomes useless when users back up to iCloud

Whatsapp currently only offers end-to-end encryption for Android devices, and only for one-to-one texts. Photos, videos or group messages are not included. However, Whatsapp services millions of users, so this measure still amounts to a large-scale operation. The company also plans to cover iOS as well, though an exact date hasn’t been disclosed. 

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The move follows announcements by Apple and Google, who both pledge to encrypt iPhone and Android data by default. 

Whatsapp’s new approach lines up with what founder Jan Koum has long desired—a chat system too secure for powerful governments to snoop on. Raised in Ukraine, Koum frequently and publicly denounced attempts to extract surveillance data from Whatsapp. 

“I grew up in a society where everything you did was eavesdropped on, recorded, snitched on,” Koum told Wired UK. “Nobody should have the right to eavesdrop, or you become a totalitarian state—the kind of state I escaped as a kid to come to this country where you have democracy and freedom of speech. Our goal is to protect it.”