What NFC protocol is used to read information on a Passport?

Information in passports is protected by the Basic Access Control protocol, the standard can be found here. In order to read from the passport you need certain pieces of information; the passport number, the D.O.B and the date of expiry.

NFC TagInfo is quite a nice app that can read passports amongst other things, make sure you enter the correct information before attempting the read though. It can take a few seconds to read due to the amount of information being transferred.

In the USA there are foil covers over the passport which prevent the NFC working without the passport being open however with my UK passport I can read it just fine when it's closed.

These following posts: 1 & 2 has some high-level information on the steps that you have to go through. It describes the steps through the use of an NFC tag reading app, but the steps look to include. First identifying the tag and making an attempt to read. The read requires information fromthe passport to decrypt the stored data. Hope this helps some.