<https://www.nytimes.com/2019/07/26/technology/hong-kong-protests-facial-reco...> HONG KONG — The police officers wrestled with Colin Cheung in an unmarked car. They needed his face. They grabbed his jaw to force his head in front of his iPhone. They slapped his face. They shouted, “Wake up!” They pried open his eyes. It all failed: Mr. Cheung had disabled his phone’s facial-recognition login with a quick button mash as soon as they grabbed him. As Hong Kong convulses amid weeks of protests, demonstrators and the police have turned identity into a weapon. The authorities are tracking protest leaders online and seeking their phones. Many protesters now cover their faces, and they fear that the police are using cameras and possibly other tools to single out targets for arrest. And when the police stopped wearing identification badges as the violence escalated, some protesters began to expose officers’ identities online. One fast-growing channel on the social messaging app Telegram seeks and publishes personal information about officers and their families. The channel, “Dadfindboy,” has more than 50,000 subscribers and advocates violence in crude and cartoonish ways. Rival pro-government channels seek to unmask protesters in a similar fashion. Mr. Cheung, who was arrested last week on a suspicion of “conspiring and abetting murder,” subscribes to the “Dadfindboy” channel, although he denied being among its founders as the police have said and he condemned posts calling for violence. He believes he was targeted by the police because he developed a tool that could compare images against a set of photos of officers to find matches — a project he later abandoned. Interested in All Things Tech? The Bits newsletter will keep you updated on the latest from Silicon Valley and the technology industry. “I don’t want them to be like secret police,” said Mr. Cheung, who was released on bail and has not been charged with wrongdoing. “If law enforcement officers don’t wear anything to show their identity, they’ll become corrupt. They’ll be able to do whatever they want.” “With the tool, ordinary citizens can tell who the police are,” he added. Hong Kong is at the bleeding edge of a significant change in the authorities’ ability to track dangerous criminals and legitimate political protesters alike — and in their targets’ ability to fight back. Across the border in China, the police often catch people with digital fingerprints gleaned using one of the world’s most invasive surveillance systems. The advent of facial-recognition technology and the rapid expansion of a vast network of cameras and other tracking tools has begun to increase those capabilities substantially. The transformation strikes a strong chord in Hong Kong. The protests began over a proposed bill that would have allowed the city to extradite criminal suspects to mainland China, where the police and courts ultimately answer to the Communist Party. [...]