The passphrases are some words from the title of the last portal of the previous mission. Exceptions are:
1. In mission where the first portal is "monument to the fallen pilots" password is actually "pilot" despite the fact that the game shows 'pilot".
2. In mission 13 password is "concert" despite it showing nothing in mission 13.
There is one portal at the cemetery. It is closed at night but the gate was not locked for me, I'm not sure whether it was intended. Otherwise this banner is accessible 247.