China had about 176 million surveillance cameras in operation as of 2016. By 2022, the number is expected to reach 2.76 billion, in a country with a population of 1.4 billion, according to IDC, a market intelligence company.

The technology, which uses biometric computer applications to automatically identify an individual from a database of digital images, is already being deployed at US airports.

In China, for example, facial recognition is now being used not just at border checkpoints, but…