The border agent swipes the data page through a special reader to read the two lines of printed characters on the bottom of the data page. This provides a digital key, a signed document, that’s unique to your passport and required in the next step.
When the passport is held over the electronic passport reader (no contact is necessary), a radio field enables the reader to communicate with the chip. The chip checks that the digital key is correct, then transmits the encrypted data to the reader. The reader confirms the epassport is authentic and the border officer conducts his visual checks.