Since the early 1990s, engineers have proposed many mechanisms for providing confidential communications and data integrity in mobile ad hoc networks (MANET). The deficiency of fastened infrastructure makes mobile ad hoc networks more vulnerable to security threats than conventional wireless networks. MANET can be considered as a short-lived collection of mobile nodes that communicate with each other in between. All involved nodes in the network system share the responsibility for routing, accessing, and communicating. The main challenges on the design of MANET include high power saving and low bandwidth. The public key infrastructure (PKI) is a well-known mechanism used to provide data integrity and confidential communications in MANET recently. The computation loads of PKI, however, are heavy to each mobile node in the cluster. Without adopting PKI cryptosystems to en/decrypt messages, we propose a novel version based on a variant Diffie--Hellman protocol. The novel method can preserve the forward and backward secrecy of group communications. Specifically, the new method outperforms related works in the computation overheads of involved nodes while communicating with other nodes.
