A method and apparatus for establishing security associations between nodes of an ad hoc wireless network includes two authentication steps: an initial first contact step (authentication, authorization, and accounting (AAA)-based authentication), and a “light-weight” step that reuses key material generated during first contact. A mesh authenticator within the network provides two roles. The first role is to implement an 802.1X port access entity (PAE), derive transient keys used for encryption with a supplicant mesh point via a four-way handshake and take care of back end communications with a key distributor. The second role is as a key distributor that implements a AAA-client and derives keys used to authenticate a mesh point during first contact or fast security association. The key distributor and the on-line authentication server can communicate to one another without these messages being transported over mesh links.