Encrypted messaging app Sign seems to be blocked in China

The Signal Messenger app is displayed on a smartphone in Hong Kong, China.

Roy Liu | Bloomberg | Getty Images

GUANGZHOU, China – Encrypted messaging app Signal has stopped working in China and is now only accessible through a virtual private network (VPN).

China blocks many foreign apps and services, including those from Facebook and Google. But Signal hadn’t previously been blocked by the so-called Great Firewall.

Signal claims to be end-to-end encrypted, which means that neither the company nor outsiders can view the content of messages between a sender and the intended recipient. This also means that authorities cannot intercept messages.

CNBC tested Signal on three different devices and messages did not come through, suggesting it was blocked by authorities. The app was still available for download from Apple’s Apple App Store.

The signal was not immediately available for comment when contacted by CNBC.

However, the messaging app continued to work when used with a VPN. A VPN, or virtual private network, allows users to protect privacy and bypass internet restrictions by connecting to servers around the world.

The signal that is being blocked in China underscores increasing internet censorship in the world’s second largest economy.

Signal’s downloads rose sharply earlier this year after rival WhatsApp changed its terms of use to allow some data to be shared with parent company Facebook.

According to the Sensor Tower, the signal in China is relatively low with 510,000 downloads from the Apple App Store so far. However, the app offered a rare way to send encrypted messages over a foreign platform without a VPN.

Still, the dominant messaging app in China, WeChat, remains Tencent-owned with over a billion users.

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