The purpose of this scheme is to detect unreliable node from routing and provide reliable data transmission in MANET. The openness in network topology and deficiency of the central administration leads to vulnerable attack in MANET. In order to decrease the threat in Mobile Ad-hoc Network (MANET), we propose Unreliable node Detection by Elliptical Curve Diffe-Hellman in MANET (UD-ECDH). The UD-ECDH scheme exchanges the secret key to detect the unreliable node and isolate from routing thus increasing the network performance. Improvement: The simulation results show that this scheme assure better packet delivery, improve throughput, reduces the delay and energy consumption in the network.