“The facial recognition software provides the [CBP Officers] with a match confidence score after the e-passport chip is scanned and the photo is taken. The score is generated by algorithms designed to detect possible imposters.”A one-to-one search comparing the passport photo to the person standing at the customs kiosk is about as simple as a facial recognition deployment gets.
The only complicating factor is where they get the photo. If they use the photo physically present on the passport's photo page, they will probably want to contend with the security marks and holograms somehow while processing the image for matching. If they want to use the photo stored electronically on the passport's internal chip, as it appears they do, they'll need some specialized hardware that retrieves the photo and the issue of "broken" passports will arise. Still, as far as country-level biometric deployments go, this one isn't too daunting.
In a post-pilot phase, it may be desirable to use the passport number to pull the photo from a State Department database and compare that to the passport image and a live image of the person presenting their travel documents.
