Mafia-type game which a secret message is communicated
Not a perfect fit, but it sounds a bit like Speakeasy, a party game in which you use a secret password to identify your teammates and try to deduce as much as you can about the other side, including their passwords and roles etc.

There are two sides (Feds and Mob) which are equally balanced and the game includes roles and "powers" which mix things up a lot.