A system and methods providing immediate peer-to-peer messaging between mobile devices in a wireless system. An invitation architecture is disclosed which enables the exchange of personal identification numbers (PINs) without requiring a user to directly access or provide his or her PIN. A messaging application encrypts its associated PIN before providing it to a messaging application on another mobile device through an existing communication application. An invitation process for exchanging encrypted PINs involves receiving an invitation containing a question, obtaining user input of an answer, and transmitting the answer back to the sender with an encrypted PIN. The sender confirms the received answer is correct and replies with its encrypted PIN.