Abstract: In Crowds，an anonymous browsing system，on the premise of having slight effect on the level of anonymity degree，improves the system performance by decreasing forwarding probability to reduce the length of rerouting paths.This paper proposes a method to confirm the decreasing proportion quotiety using the discipline that the expected length of a path descending.Simulation result shows that the method can improve effectively the performance with reducing the length of rerouting path，while keep the anonymity at the same level.

Key words: anonymous communication, Crowds, predecessor attack

摘要： Crowds匿名浏览系统中可以在不影响匿名度水平的前提下，通过递减转发概率减小重路由路径长度，提高系统性能。提出利用路径长度期望值递减规律确定转发概率递减比例系数的方法，仿真实验表明，新方案可以在保持原有匿名度的基础上，有效减小重路由路径长度，提高Crowds系统的通信性能。

关键词: 匿名通信, Crowds, 前驱攻击