The secure chat app Signal has become the most downloaded app in Hong Kong on both Apple’s and Google’s app stores, Bloomberg reports, citing data from App Annie. The surging interest in encrypted messaging comes days after the Chinese government in Beijing passed a new national security law that reduced Hong Kong’s autonomy and could undermine its traditionally strong protections for civil liberties.

The 1997 handover of Hong Kong from the United Kingdom to China came with a promise that China would respect Hong Kong’s autonomy for 50 years following the handover. Under the terms of that deal, Hong Kong residents should have continued to enjoy greater freedom than people on the mainland until 2047. But recently, the mainland government has appeared to renege on that deal.

Civil liberties advocates see the national security law approved last week as a major blow to freedom in Hong Kong. The New York Times reports that “the four major offenses in the law—separatism, subversion, terrorism and collusion with foreign countries—are ambiguously worded and give the authorities extensive power to target activists who criticize the party, activists say.” Until now, Hong Kongers faced trial in the city’s separate, independent judiciary. The new law opens the door for dissidents to be tried in mainland courts with less respect for civil liberties or due process.

This has driven heightened interest among Hong Kongers in secure communication technologies. Signal offers end-to-end encryption and is viewed by security experts as the gold standard for secure mobile messaging. It has been endorsed by NSA whistleblower Ed Snowden.

One of Signal’s selling points is that it minimizes data collection on its users. When rival Telegram announced it would no longer honor data requests from Hong Kong courts, Signal responded that it didn’t have any user data to hand over in the first place.

Bloomberg has also reported on the surging adoption of VPN software in Hong Kong as residents fear government surveillance of their Web browsing.