Mobile Ad-hoc Network (MANET) is an appealing technology that has attracted lots of research efforts over past years. Although the principle of wireless, structure-less, dynamic networks is attractive, there are still some major flaws that prevent commercial expansion. Security is one of these main barriers; MANETs are known to be particularly vulnerable to security attack. One solution proposed to increase security resilience is to use multipath routing algorithms [1]. However multipath routing also introduces new challenges in terms of security and security overhead.

In this paper we consider the problem of secure routing in fully distributed MANETs using multipath routing. After studying the effect of multipath in terms of security, we propose an efficient multipath heuristic and a new approach to protect the route discovery called SDMSR to secure the routing protocol while mitigating security overhead.