Research On Key Management Of Wireless Mobile Ad Hoc Network

Ad Hoc network is a multi-top temporarily self-organized and autonomous system without infrastructure, and is composed of mobile nodes with radio equipment for sending and receiving messages. The PRNET (Packet Radio Network), i.e., enabling the message exchange to work without the limitation of fixed or wired infrastructure, was derived from a research funded by USA military in 1970s. One of the initial motives of the PRNET was to meet the military needs for battlefield survival. With the disclosure of some techniques in the middle of 1990s, with the price deduction of high-performance mobile terminals equipped with wireless sending and receiving equipment and subsequent popularity, and with the increasing needs for individual communication, Ad Hoc network has also been applied in civil fields. In a word, with the development of mobile communication techniques and mobile terminal techniques, Ad Hoc networks has begun to be a public research focus in the field of mobile communication.Ad Hoc network takes wireless signals as the carrier of information. Wireless signal possesses the property of nondirectional divergence, and with that property, any node in the signal coverage area can freely receive the signals that nodes send, by means of passively monitoring. The information transmitting in Ad Hoc network must be encrypted in order to guarantee that only legal Ad Hoc nodes has the ability to acquire the real information. That incurs the issue of the nodes'key management in Ad Hoc network.The nodes in Ad Hoc network have mobility; meanwhile, the nodes can enter or exit the network at any time. Those lead to the result that topology of the Ad Hoc network is dynamic. Those factors determine that the key management schemes used in wired network can not be used directly in Ad Hoc network, which increases the complexity of the key management. How to decrease the communication cost in key management and the storage cost of nodes has become an important problem.Firstly, since the wireless bandwidth of Ad Hoc network is limited and the quality of wireless channel is not good, temporary falling line is not avoidable for the nodes in the Ad Hoc network, i.e. temporary communication loss with Ad Hoc network. When such nodes connect again with Ad Hoc network, they may have missed some historical important key information, and may need to communicate with management nodes to acquire current key information and the missed historical key information. As a result, both the burden of the management nodes and the network communication flux are increased. When there are many of such nodes, they request to the management nodes in a period of time simultaneously, which results in the occupation to the fragile wireless bandwidth. When the occupation is accumulated to a certain extent, DDos attack can occur. Here, it should be figured out that management node do not mean single node. Actually, they mean the nodes possessing management function. They can be one single node or multi-nodes. This paper proposed three solutions to this problem. They are: self-healing key distribution scheme based on dual directional hash chain, self-healing key distribution scheme based on sliding windows and self-healing key distribution scheme for anti-collusion attack.Self-healing key distribution scheme based on dual directional hash chain makes legal nodes to gain correct communication group key and illegal nodes to gain wrong communication group key, which renders the attack meaningless.Self-healing key distribution scheme based on sliding windows is mainly directed to the circumstance that node lifetime spans two management areas. Through the sliding windows technique, the scheme decreases the burden of management nodes and cost of network communication.Current self-healing key distribution schemes based on Hash chain structure can not resist completely the case of collusion attack to group keys by revoked nodes and newly joined nodes. According to the problem, this paper proposed a self-healing key distribution solution for anti-collusion attack.Secondly, because of the openness of Ad Hoc network, nodes can enter or exit the network at any time. Thus, the authentication of the nodes'identity should be guaranteed that the identity of node is real and valid. This paper proposed a key distribution solution in an elliptic curve field, based on identity authentication. The Ad Hoc communication key can only be acquired by those with legal identity and having secret nodes. Meanwhile, with identity authentication, fake nodes can be identified and can be expelled from Ad Hoc network.