Crowds系统中基于递减转发概率的路长控制策略

Crowds匿名浏览系统中，基于固定的转发概率建立重路由路径用以在主机间转发用户请求，从而隐藏通信的发起者．在系统所采用的转发概率较大的情况下，产生的重路由路径过长，导致转发请求的延时以及系统中成员负载等性能开销过大．文中提出基于递减转发概率的路长控制策略，用以有效控制重路由路径长度，提高传输性能．首先证明在前趋攻击下，恶意成员攻破匿名保护所需的时间轮数，主要由系统中恶意成员数目所决定，受重路由路径长度的影响较小．基于该分析结果，提出了基于递减转发概率的路长控制策略．仿真结果表明，新策略能缩短重路由路径的长度，从而在保持系统匿名保护能力的前提下，有效提升系统的性能．

Decreased Forwarding Probability Based Length Control Strategy of Crowds

In Crowds, an anonymous browsing system, rerouting paths were established basing on a fixed forwarding probability to forward requests among hosts to hide the identity of communication initiators. The length of rerouting paths became too long if the forwarding probability adopted is high, which results in high communication delay and participant payload. In this paper, a new length control strategy basing on a decreased forwarding probability is proposed for controlling the length of rerouting path. Firstly, it is analyzed theoretically that the number of rounds for collaborators to compromise the system by predecessor attack is determined mainly by the number of collaborators in the system, while effected by the length of rerouting path slightly. Based on the analysis, the decreased forwarding probability based length control strategy is proposed for establishing shorter rerouting paths. Simulation result shows that Crowds system can be improved effectively in performance with the new strategy, while keep the anonymity at the same level.