Signal Messenger is displayed on a smartphone in Hong Kong, China.
Roy Liu | Bloomberg | Getty Images
GUANGZHOU, China – The Signal encrypted messaging application no longer works in China and is now only accessible through a virtual private network (VPN).
China blocks many foreign applications and services, including Facebook and Google. But Signal had not previously been banned by the so-called Great Firewall.
The signal states that it is encrypted from one end to the other, which means that the company itself and outsiders cannot view the content of messages between a sender and the desired recipient. It also means that the authorities cannot hide the messages.
CNBC tested Signal on three different devices and the messages did not pass, suggesting it was blocked by authorities. The application was still available for download through the Apple App Store in China.
The signal was not immediately available for comment when contacted by CNBC.
However, the messaging application still worked when used with a VPN. A VPN or virtual private network allows users to protect privacy and circumvent internet restrictions by connecting to servers around the world.
The blocked signal in China highlights the growing censorship of the Internet in the world’s second largest economy.
Signal downloads rose earlier this year after rival WhatsApp changed its terms of service to allow data sharing with parent company Facebook.
The signal is relatively small in China, with 510,000 downloads so far from the Apple App Store, according to Sensor Tower. But the app has provided a rare way to send encrypted messages over a foreign platform without a VPN.
However, China’s dominant messaging application remains Tencent-owned WeChat, with over a billion users.