All existing routing protocols of Mobile Ad Hoc networks assume that IP addresses of hosts are already configured before they join the network. Some papers proposed solutions to allow an automatic configuration of nodes, i.e. without human intervention. Unfortunately these processes, often inspired of the traditional wired networks, are not always well adapted to the MANET model and appear relatively resources greedy. Moreover, they apply only to ideal networks in which all nodes can trust each other. In this manner, they do absolutely not consider the security aspects and are thus not adapted to a real use. In this paper, we propose a node auto-configuration algorithm which uses the Buddy systems technique to allocate the addresses, as well as a scheme allowing to authenticate the participants inside the network.