Two weeks ago, Kakao Talk users in South Korea users got an unpleasant surprise. After months of enduring public criticism, President Park Geun-Hye announced a crackdown on any messages deemed as insulting to her or generally rumor-mongering — including private messages sent through Kakao Talk, a Korean messaging app akin to WhatsApp or iMessage. Prosecutors began actively monitoring the service for violations, promising punishment for anyone spreading inappropriate content.

1.5 million South Koreans have signed up for Telegram in the past seven days

In response to the crackdown, South Koreans have voted with their feet, heading en masse to encrypted chat programs hosted outside the country, particularly an app called Telegram known for its encryption features. Based in Germany, Telegram reports roughly 1.5 million new South Korean users have signed up in the past seven days, giving the app more than 50 million users worldwide. Telegram's Markus Ra says it's not the only country where government controls have made Telegram an attractive option. "People frequently come to Telegram looking for extra security — some of them from countries with censorship issues," Ra says. "What really makes us happy is that the users stay when the privacy scandals have died away."

Telegram offers an option for "secret chats" that use end-to-end encryption, which means that the company facilitates key exchange but doesn't hold the keys itself and can't decrypt any of the messages. Created by Russian-born entrepreneur Pavel Durov, the app’s offshore location makes legal compulsion much more difficult for South Korean prosecutors. Telegram’s South Korean user base is still just a fraction of Kakao's 35 million users — the vast majority of cell-phone owners in South Korea — but the rapid growth shows how much privacy features can pay off in the face of high-profile censorship.

Kakao Talk has struggled to provide the same privacy promises. Since the crackdown was announced, the company has faced rumors that prosecutors are reading chats in real-time, even though the company insists such a setup would be technically impossible. On Thursday, the company announced it would curtail its storage practices, only keeping messages for three days after they're sent, rather than a full week. Still, since Kakao is based in Korea, it can only push back so far. The company is obligated to comply with court orders under South Korean law, turning over messaging data as prosecutors demand it.

But while companies compete for user privacy, government pushback isn't unique to South Korea. When Apple took a step towards Telegram-esque end-to-end encryption last month, the FBI pushed back immediately, claiming the features would aid criminals and hinder legitimate warrants. Apple’s supporters responded simply that, after Snowden, the company was giving its users what it wanted. After Telegram’s sudden rise, it’s a more convincing argument than ever.

Sojung Lim contributed reporting