隨著無線感測網路廣泛運用在軍事與民間上，安全已經成為一項非常重要的議題。Sybil 攻擊是藉由單一的惡意節點非法的偽造許多假的、不存在的節點資訊來欺騙週遭的鄰居，使得它們誤認這些假的節點為它們的鄰居，進而擾亂整個網路。之前的解決方法中大部分是將每個節點分配一些鑰匙 (encryption keys)，利用這些鑰匙來對彼此認證，以確定彼此都是真實存在的節點。本篇論文提出了一個偽造節點的偵測機制，不需使用任何的鑰匙、類似的機密訊息、特殊的硬體、或是輔助節點。主要的方式是利用每個節點周遭鄰居的差異性來判斷。在數學分析與實驗結果顯示若在節點密度足夠的情況下，本方法可以達到非常理想的偵測率並減低錯誤的判斷。

As widely used in the military and civilians, security has become an important issue in Wireless Sensor Networks (WSNs). The Sybil attack is a notorious attack in sensor and peer-to-peer networks. In the Sybil attack, a malicious node illegitimately claims a lot of identities to other nodes and try to disturb the networks by those forged identities. Most previous solutions focus on authentication-based mechanisms which share some encryption keys and verify the identities of each other. Different from previous solutions, this thesis proposed a method which need not share any keys or keep any secret information to authenticate the node's identities. The idea is to verify the differences in neighboring nodes of each node. The mathematical analysis results showed that the mechanism performs well while the node density is high enough and the simulation results also showed that the method could identify more than 99% Sybil nodes with little false detection.

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