Encrypted Messaging App Signal Goes Down in China

Signal, the popular encrypted messaging app, stopped working in China on Tuesday, according to multiple reports. The app is still available in the Apple App Store in China, according to Reuters, but it’s not clear how much longer that might last.

The Chinese government has not made any announcement about Signal being blocked or banned in China, but Signal’s website was unavailable in the country starting on Monday. Google’s Play Store is unavailable in China, but Android users could previously download the app directly from Signal’s website.

Signal did not immediately respond to questions emailed early Tuesday.

Text message verification codes for Signal are not working in China at the moment, according to users who are discussing the outage on Twitter, which would make new sign-ups for the service impossible for anyone using a phone number in mainland China. Some users were still able to access Signal if they turned on a VPN.

Signal is reportedly still working in Hong Kong, a region that’s was largely autonomous from the Chinese government before a crackdown in recent months largely destroyed the “one country, two systems” approach to governance.

China has totaled over 500,000 downloads of Signal on iOS, according to TechCrunch, though that’s a relatively humble number in a country of 1.4 billion people. But Signal’s growth was likely concerning for Chinese authorities who attempt to monitor and control everything done on the internet in mainland China. Signal’s end-to-end encryption would have made it extremely difficult to monitor communications between two people on the app.

Signal was developed by Open Whisper Systems, and has plenty of baggage since it has ties to the U.S. intelligence community. But that origin story alone makes it somewhat surprising Signal was allowed inside China in the first place. WeChat, which is not end-to-end encrypted, is by far the most popular messaging app in China.