A Vehicular Ad-Hoc Network, or VANET, is a form of Mobile Ad-Hoc Network to provide communications among nearby vehicles and between vehicles and nearby fixed equipments. Security has become a prime concern in providing communication between these vehicles. Unlike wired networks, the characteristics of Vehicular Ad Hoc Networks (VANETs) pose a number of non-trivial challenges to security design. In this paper, the authors present a threshold security mechanism with a mobility based Clustering for Open Inter Vehicle Communication Networks (COIN). Nodes that have a similar moving pattern are grouped into a cluster, and unlike other clustering algorithms, it takes the moving pattern of the vehicles into consideration with the driver’s intention. The stability of clusters is estimated based on relative mobility of cluster members. A threshold cryptographic scheme is employed on top of the clusters to protect routing information and data traffic. To ensure distributed trust in the clustered environment, the private key (k) is divided into n pieces in such a way that k is easily reconstructable from any p number of pieces.