Mobile ad hoc networks (MANETs) are very useful in various scenarios where there is need of fast deployment of the network and expensive set up is not required. With these benefits, there are some issues related to these networks. One of these issues is of secure communication. Malicious nodes can easily attack existing routing protocols for MANETs like DSR. In this paper we have proposed a modification of DSR by using message digest. The proposed work produces better results in terms of different metrics when compared with the results of DSR. When a route is set up between the two communicating mobile nodes, the data is sent through a secure key which is not impossible for the intruder nodes to intercept. This halts intrusion in the network. A message digest is created of the data packets.