In this paper we propose a decentralized privacy- preserving scheme for mobile ad hoc networks (MANETs), where nodes establish security associations. In order to achieve privacy and security, we use homomorphic encryption and polynomial intersection so as to find the common friends of two nodes. Through our experimental results we verify the correctness of our scheme given the limitations of MANETs. Keywords-Trust; Homomorphic Encryption; Reputation Sys- tem; Mobile Ad hoc Networks;