Abstract: In mobile ad hoc networks，nodes cooperate by forwarding packets for each other to allow them to communicate.The cooperation of nodes is very important.With lack of a prior trust relationship，the cooperative security schemes offer the effective solution to resolve the uncooperative behavior which launched by the malicious and selfish nodes in the mobile ad hoc networks.we present that an Optimized Local Reputation System.In our approach，reputation is exchanged in k-hop neighborhood，which not only can reduce the cost of system but also can fully learn the experiences from its neighbors.Binary Exponential Backoff Algorithm is adopted to deal with the uncooperative nodes.Our approach can effectively inspirit the nodes to cooperate，and enhance the performance of mobile ad hoc networks.

Key words: mobile Ad hoc networks, network security, reputation system, cooperation

摘要： 移动自组网节点间的通信由多个节点相互协作来共同完成，节点合作与否是实现通信的关键。在缺少预先约定的信任关系时，合作性的安全机制是解决网络内部恶意节点和自私性节点不合作行为的有效方法。提出了一种优化的局部声誉值合作性方案，该方案只在k跳邻居内交换声誉值，系统开销小，并能充分学习邻居的经验。采用二进制指数后退算法对不合作节点进行处置，能有效激励节点的合作性，提高网络的性能。

关键词: 移动自组网, 网络安全, 声誉系统, 合作性