In this paper, we propose a new architecture based on an efficient trust model and clustering algorithm in order to distribute a certification authority (CA) for ensuring the distribution of certificates in each cluster. We use the combination of fully self-organized security for trust model like PGP adapted to ad-hoc technology and the clustering algorithm which is based on the use of trust and mobility metric, in order to select the clusterhead and to establish PKI in each cluster for authentication and exchange of data. Furthermore, we present new approach Dynamic Demilitarized Zone (DDMZ) to protect CA in each cluster. The principle idea of DDMZ consists to select the dispensable nodes, also called registration authorities; these nodes must be confident and located at one-hope from the CA. Their roles are to receive, filter and treat the requests from any unknown node to CA. With this approach, we can avoid the single point of failure in each cluster. This architecture can be easily extended to other hierarchical routing protocols. Simulation results confirm that our architecture is scalable and secure.