Wireless mesh networks (WMNs) are currently accepted as a new communication paradigm for next-generation wireless networking. They consist of mesh routers and clients, where mesh routers are almost static and form the backbone of WMNs.Several architectures have been proposed to distribute the authentication and authorization functions in the WMN backbone. In such distributed architectures, new mesh routers authenticate to a key management service (consisting of several servers, named core nodes), which can be implemented using threshold cryptography, and obtain a temporary key that is used both to prove their credentials to neighbor nodes and to encrypt all the traffic transmitted on wireless backbone links.This paper analyzes the optimal placement of the core nodes that collaboratively implement the key management service in a distributed wireless security architecture. The core node placement is formulated as an optimization problem, which models closely the behavior of real wireless channels; the performance improvement achieved solving our model is then evaluated in terms of key distribution/authentication delay in several realistic network scenarios.Numerical results show that our proposed model increases the responsiveness of distributed security architectures with a short computing time, thus representing a very effective tool to plan efficient and secure wireless networks.