Question: I'm experimenting with NFC and realized that my passport actually stores data that is only available when the passport is opened. (A closed passport doesn't seem to divulge any information)

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> What sequence of instructions is required to read data from a passport? 
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I assume a passive reading is insufficient, and some challenge / response is required. (I base this on how existing 3rd party NFC applications interact with passport data)

Answer: 
Information in passports is protected by the [Basic Access Control](http://en.wikipedia.org/wiki/Basic_access_control) protocol, the standard can be found [here](http://icao.int/publications/pages/publication.aspx?docnum=9303) (Updated from Wojciech's comment). 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](https://play.google.com/store/apps/details?id=at.mroland.android.apps.nfctaginfo&hl=en) 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](http://en.wikipedia.org/wiki/United_States_passport#Biometric_passport) without the passport being open however with my UK passport I can read it just fine when it's closed.
These following posts: [1](http://randomoracle.wordpress.com/2012/08/27/reading-the-us-passport-using-an-android-phone-overview/) & [2](http://www.flyertalk.com/forum/travel-technology/1342167-viewing-info-epassport-chip-using-android-phone-nfc.html) 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.