The IEEE 802 standards ease the deployment of networking infrastructures and enable employers to access corporate networks while traveling. These standards provide two modes of communication called infrastructure and ad-hoc modes. A security solution for the IEEE 802.11's infrastructure mode took several years to reach maturity and firmware are still been upgraded, yet a solution for the ad-hoc mode needs to be specified. The present paper is a first attempt in this direction. It leverages the latest developments in the area of password-based authentication and (group) Diffie-Hellman key exchange to develop a provably-secure key-exchange protocol for IEEE 802.11's ad-hoc mode. The protocol allows users to securely join and leave the wireless group at time, accommodates either a single-shared password or pairwise-shared passwords among the group members, or at least with a central server; achieves security against dictionary attacks in the ideal-hash model (i.e. random-oracles). This is, to the best of our knowledge, the first such protocol to appear in the cryptographic literature.