In mobile adhoc networks, generating and maintaining anonymity for any adhoc node is challenging because of the node mobility, dynamic network topology, cooperative nature of the network and broadcast nature of the communication media. Anonymity is provided to protect the communication, by hiding the participants as well as the message contents. Existing techniques based on cryptosystem and broadcasting cannot be easily adapted to MANET because of their extensive cryptographic computation and/or large communication overhead. In this paper, we first propose an unconditionally secure privacy preserving message authentication scheme (PPMAS) which uses Modified New variant ElGamal signature Scheme (MNES). Secondly we proposed privacy preserving communication protocol for MANET based on dynamic generation of pseudonyms, which are used in place of real nodes to provide anonymity.