> It’s just a bar code that guy scans to retrieve the official record with photo ID on their server.

This would require a fully connected graph between all Departments of State around the world (i.e., the holders of their respective countries' passport DBs), and that is definitely not the case. It will also never be the case, since there are various geopolitical advantages to having a secret passport database (like being able to mint identities for spies, or deny the existence of a person).

The bar code you're referring to is just a machine-readable version of the information printed on the paper. It doesn't carry any proof of authenticity.

Just FYI they do contain machine readable digital signatures from the passport issuer these days.

Is that in the RFID tag? I know US passports have those embedded, but I wasn't sure about other nationalities.

I'd be curious to learn more about how they verify those signatures as well; I can imagine it being nontrivial/de facto limited to a collection of trusted partner nations.

They definitely do have it in the RFID tag. Depending on your nationality, some have it printed in a larger QR-code like thing, I think. There’s an international standard, but I wouldn’t know where to find it.

It's specified by IATA. It's an NFC tag, not RFID, and the data is a JPEG2000 image with its hash embedded inside an X.509 certificate. There's no public root store: the national root certs are passed around between governments using diplomatic bags.

The standards are all public and anyone can write an app to verify e-Passports. There are Android apps on the Play Store that can do it, although they don't necessarily have complete collections of national certs.

FWIW, the ICAO standard[1] mentions ISO 14443 for communication, which (seems) to only cover RFID and not NFC.

[1]: https://www.icao.int/publications/Documents/9303_p9_cons_en....

NFC is a superset of RFID I think. At least, you can read the tags with the NFC tag functionality of a smartphone.

Edit: oops yes you're right I meant ICAO, IATA is a different airline related organization.

If only that was how it worked. Even within the country of origin they don't always have access to such a system easily, let alone between countries.

A nosy customs official can flip through the other stamps in the passport to see if you've been some place that makes you suspect. Also, certain countries will tag your passport which marks you for automatic extra inspections without even looking at your photo/name info. This happened to me specifically in Australia.

That's actually one of the specific exceptions that you can use in the U.S. to get a second passport issued, in case you need to travel to countries which are in conflict with one another.