Securing ad hoc networks is a challenging task due to their specific characteristics. One of the major challenges is that ad hoc networks typically lack a fixed infrastructure both in form of physical nodes such as routers, servers, and stable communication links and in the form of an organizational or administrative infrastructure. New nodes can hence, join and leave the network at any time, which appeals to an efficient and flexible trust establishment mechanism. We propose in this paper an efficient protocol for key management in ad hoc networks relying on the routing mechanism itself.