[quote=chukklehed]
I meant in secret. You know, since they have to stay hidden? They have to have some way to tell if they're talking to a member of the rebellion or not.
[/quote]

They've had a long time to determine friend from Empire supporter, I imagine the Hokage and Mizukage both managed to inspire loyalty from the people that worked to see their villages flourish and freed from Empire control. If anything, if you don't know them, be careful of what you say.

If it really gets complicated, I'll set up some sort of password between villages, but Kirigakure and Konoha are generally full rebel in faction, sympathizers and supporters of the Empire are generally harassed out of the village. Hokage and Mizukage tried to root out those types before they took on the Empress.