[1] says the decryption key is derived from those pieces of information, and the key derivation logic is public info, e.g. [2] is an implementation.

It's somewhat clever, if someone takes a photo of the first page, they already have your personal info, to steal it from the chip they still need to have visual on the info on that page.

[1] https://randomoracle.wordpress.com/2012/08/27/reading-the-us...

[2] https://github.com/AndyQ/NFCPassportReader/blob/main/Example...