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. The invitation architecture automatically manages the encryption, any requisite key exchanges, the composition of invitation and acceptance messages, and the decryption and storage of PINs.