Until recently, Hoan Ton-That's greatest hit was an app that let people put Donald Trump's distinctive yellow hair on their own photos.
Then Ton-That did something momentous: He invented a tool that could end your ability to walk down the street anonymously and provided it to hundreds of law enforcement agencies.
His tiny company, Clearview AI, devised a groundbreaking facial recognition app. You take a picture of a person, upload it and get to see public photos of that person along with links to where those photos appeared. The system - whose backbone is a database of more than 3 billion images that Clearview claims to have scraped from Facebook, YouTube, Venmo and millions of other websites - goes far beyond anything ever constructed by the US government or Silicon Valley giants.
Federal and state law enforcement officers said that while they had only limited knowledge of how Clearview works and who is behind it, they had used its app to help solve shoplifting, identity theft, credit card fraud, murder and child sexual exploitation cases.
Until now, technology that readily identifies everyone based on their faces has been taboo because of its radical erosion of privacy.
But without public scrutiny, more than 600 law enforcement agencies have started using Clearview in the past year, according to the company, which declined to provide a list. The computer code underlying its app, analysed by The New York Times, includes programming language to pair it with augmented reality glasses; users would potentially be able to identify every person they saw.
Clearview has also licensed the app to at least a handful of companies for security purposes.
"The weaponisation possibilities of this are endless," said Eric Goldman, co-director of the High Tech Law Institute at Santa Clara University. "Imagine a rogue law enforcement officer who wants to stalk potential romantic partners, or a foreign government using this to dig up secrets about people to blackmail them or throw them in jail."
Clearview has shrouded itself in secrecy, avoiding debate about its boundary-pushing technology. When I began looking into the company in November, its website was a bare page showing a nonexistent Manhattan address as its place of business. The company's one employee listed on LinkedIn, a sales manager named "John Good," turned out to be Ton-That, using a fake name. For a month, people affiliated with the company would not return my emails or phone calls.
While the company was dodging me, it was also monitoring me. At my request, a number of police officers had run my photo through the Clearview app. They soon received phone calls from company representatives asking if they were talking to the media - a sign that Clearview has the ability and, in this case, the appetite to monitor whom law enforcement is searching for.
Facial recognition technology has always been controversial. Clearview's app carries extra risks because law enforcement agencies are uploading sensitive photos to the servers of a company whose ability to protect its data is untested.
The company eventually started answering my questions, saying that its earlier silence was typical of an early-stage startup in stealth mode. Ton-That acknowledged designing a prototype for use with augmented reality glasses but said the company had no plans to release it. And he said my photo had rung alarm bells because the app "flags possible anomalous search behaviour" in order to prevent users from conducting what it deemed "inappropriate searches."
In addition to Ton-That, Clearview was founded by Richard Schwartz - who was an aide to Rudy Giuliani when he was mayor of New York - and backed financially by Peter Thiel, a venture capitalist behind Facebook and Palantir.
Another early investor is a small firm called Kirenaga Partners. Its founder, David Scalzo, dismissed concerns about Clearview making the internet searchable by face, saying it's a valuable crime-solving tool.
"I've come to the conclusion that because information constantly increases, there's never going to be privacy," Scalzo said. "Laws have to determine what's legal, but you can't ban technology."
Ton-That, 31, grew up a long way from Silicon Valley, in his native Australia. In 2007, he dropped out of college and moved to San Francisco. The iPhone had just arrived, and his goal was to get in early on what he expected would be a vibrant market for social media apps.
In 2015, he spun up Trump Hair, which added Trump's distinctive coif to people in a photo, and a photo-sharing program. Both fizzled.
Ton-That moved to New York in 2016. He started reading academic papers on artificial intelligence, image recognition and machine learning.
Schwartz and Ton-That met in 2016 at a book event at the Manhattan Institute, a conservative think tank. Schwartz, now 61, had amassed an impressive Rolodex working for Giuliani in the 1990s. The two soon decided to go into the facial recognition business together: Ton-That would build the app, and Schwartz would use his contacts to drum up commercial interest.
Police departments have had access to facial recognition tools for almost 20 years, but they have historically been limited to searching government-provided images, such as mug shots and driver's license photos.
Ton-That wanted to go way beyond that. He began in 2016 by recruiting a couple of engineers. One helped design a program that can automatically collect images of people's faces from across the internet, such as employment sites and social networks. Representatives of those companies said their policies prohibit such scraping.
Another engineer was hired to perfect a facial recognition algorithm that was derived from academic papers. The result: a system that uses what Ton-That described as a "state-of-the-art neural net" to convert all the images into mathematical formulas, or vectors, based on facial geometry - like how far apart a person's eyes are. Clearview created a vast directory that clustered all the photos with similar vectors into "neighborhoods." When a user uploads a photo of a face into Clearview's system, it converts the face into a vector and then shows all the scraped photos stored in that vector's neighborhood - along with the links to the sites from which those images came.
Clearview remains tiny, having raised $7 million from investors, according to Pitchbook, a website that tracks investments in startups. The company declined to confirm the amount.
In February, the Indiana State Police started experimenting with Clearview. They solved a case within 20 minutes of using the app. Two men had gotten into a fight in a park, and it ended when one shot the other in the stomach. A bystander recorded the crime on a phone, so police had a still of the gunman's face to run through Clearview's app.
They immediately got a match: The man appeared in a video that someone had posted on social media, and his name was included in a caption on the video. "He did not have a driver's license and hadn't been arrested as an adult, so he wasn't in government databases," said Chuck Cohen, an Indiana State Police captain at the time.
The man was arrested and charged; Cohen said he probably wouldn't have been identified without the ability to search social media for his face. The Indiana State Police became Clearview's first paying customer, according to the company. (Police declined to comment beyond saying that they tested Clearview's app.)
The company's most effective sales technique was offering 30-day free trials to officers. Ton-That finally had his viral hit.
Federal law enforcement, including the FBI and the Department of Homeland Security, are trying it, as are Canadian law enforcement authorities, according to the company and government officials.
Ton-That said the tool does not always work. Most of the photos in Clearview's database are taken at eye level. Much of the material that police upload is from surveillance cameras mounted on ceilings or high on walls.
Despite that, the company said, its tool finds matches up to 75 per cent of the time.
One reason that Clearview is catching on is that its service is unique. That's because Facebook and other social media sites prohibit people from scraping users' images; Clearview is violating the sites' terms of service.
Some law enforcement officials said they didn't realize the photos they uploaded were being sent to and stored on Clearview's servers. Clearview tries to preempt concerns with an FAQ document given to would-be clients that says its customer support employees won't look at the photos that police upload.
Clearview also hired Paul Clement, a US solicitor general under President George W. Bush, to assuage concerns about the app's legality.
In an August memo that Clearview provided to potential customers, including the Atlanta Police Department and the Pinellas County Sheriff's Office in Florida, Clement said law enforcement agencies "do not violate the federal Constitution or relevant existing state biometric and privacy laws when using Clearview for its intended purpose."
Clement, now a partner at Kirkland & Ellis, wrote that authorities don't have to tell defendants that they were identified via Clearview as long as it isn't the sole basis for getting a warrant to arrest them. Clement did not respond to multiple requests for comment.
The memo appeared to be effective; the Atlanta police and Pinellas County Sheriff's Office soon started using Clearview.
Woodrow Hartzog, a professor of law and computer science at Northeastern University in Boston, sees Clearview as the latest proof that facial recognition should be banned in the United States.
"We've relied on industry efforts to self-police and not embrace such a risky technology, but now those dams are breaking because there is so much money on the table," Hartzog said. "I don't see a future where we harness the benefits of face recognition technology without the crippling abuse of the surveillance that comes with it. The only way to stop it is to ban it."