关键词: 发布订阅系统, 拒绝服务攻击, 订阅合并, 时间复杂度, 带宽开销

Abstract: A novel subscription merging method is proposed to deal with the Denial Of Service（DOS） attacks in publish/subscribe systems.Different from the current methods，the proposed method only merges the similar subscriptions.Thus it can reduce the bandwidth cost during event forwarding after merging compared to current methods.The judgment of the similarity of subscriptions depends on the size and the location of the constraint range of each attribute of the subscription，and grouping mechanism with two steps to group similar subscriptions is proposed.Theoretically analysis shows that the proposed method has low time complexity and can control the merging granularity dynamically according to the load of nodes，thus can efficiently deal with DOS attacks.The results from the experiments show that the proposed method only increases a little bandwidth cost during event forwarding.

Key words: publish/subscribe systems, Denial Of Service（DOS） attack, subscription merging, time complexity, bandwidth cost