Signal has become the most downloaded messaging app in Hong Kong after Beijing imposed a sweeping national security law on the city that stirred fears of curbs on civil liberties.

The app, endorsed by whistle-blower and privacy advocate Edward Snowden, provides end-to-end encryption to secure messages from being read by a third party as they travel between users. It has topped the communications category in Apple’s and Google’s mobile app stores and is the second most popular free app on both.

Hong Kong detailed on Monday unprecedented online policing powers under the new law, including warrants for “any action” necessary to remove content deemed in violation. But the nonprofit responsible for Signal said that it won’t cooperate with any requests for user data from Hong Kong courts — joining tech giants like Microsoft in the wake of the law’s passage — in part because it doesn’t collect any data to begin with.

“We never started turning over user data to HK police. Also, we don’t have user data to turn over,” it wrote on Twitter.

Signal’s privacy-first ethos includes the app’s deliberate ignorance of what its users are doing, which goes above and beyond the likes of Telegram, another secure messenger that’s been popular in Hong Kong amid protests against the Beijing government. Virtual private networks, designed to disguise a user’s digital footprints, also saw a big spike in downloads in May as plans for the national security law started to emerge from the Chinese capital.

The controversial law went into effect on 30 June and has already had a chilling effect on free expression in Hong Kong. It forbids speech and actions that might be seen as encouraging secession from China, terrorism, subversion of state power or collusion with foreign forces. Private messaging platforms have become a refuge as a result, with Hong Kongers retreating to unmonitored forms of communication. — Reported by Felix Tam, (c) 2020 Bloomberg LP