You don&#x27;t actually need to match up to the individual, you have roughly say 100 or 1000 possible candidates for each scan, based on people you processed in the last X minutes. You can just save that then all you need is 2 scans to be able to match.<p>If you&#x27;re tagging face when they get processed and running face recognition at the scanner, (which is either already possible or will be possible within a couple years) you don&#x27;t even need to do that.<p>On a related note, I feel like people dont factor in the (exponential) progress of technology in their threat assessment. For example sites that tell people their password strength don&#x27;t count Moore&#x27;s law into password difficulty calculations. Nobody uses post quantum crypto. The NSA has played this by storing as much interesting encrypted data and then decrypting it when technology progresses Or vulnerabilities are discovered. Most of our encrypted data is plain text in some X number of years.<p>Anyway going back to scanners, you could just store data and wait until computer vision gets to the point where you can do it with computers. Anything a person can do a computer will eventually be able to do. If a person could watch a bunch of camera feeds and track each person from the point he presents ID to the point he is scanned a computer will eventually be able to too.<p>IMO they already can.