隨意行動網路 (Mobile Ad-Hoc Network, MANET) 是無線網路的其中一項分支。隨意行動網路具有能快速設置、動態拓樸的節點及缺少如轉接器、無線基地台(Access Point, AP)等基礎設施等特性，這些特性讓隨意行動網路能應用於特定的場景如軍事用途、搜救或緊急行動。基於路由協定，節點互相提供連結資訊並能共同建立完整傳輸路徑。但傳輸安全一直是隨意行動網路中的一項問題，起因於隨意行動網路的特性如連結公開的網路、因此缺少安全防線、去中心化的設置及路由協定中缺乏安全考慮的設計都讓MANET比有線網路更難於管理和抵禦利用這些弱點所形成的攻擊。  
    在本研究中針對隨意行動網路最常見的女巫攻擊(Sybil Attack)來做進一步的研究，女巫攻擊可能造成封包流量改向以及其他延伸影響。我們使用 NS3模擬器來模擬一個基於共識機制的演算法拜占庭將軍問題協議(Byzantine Agreement Algorithm)來解決Sybil attack 對於隨意行動網路的威脅，確保所有原來易遭受竄改的網路節點在傳輸過程中可以保持資料的完整性。目標在沒有網路基礎架構下，仍能保持通訊安全。

The topology of mobile ad hoc networks (MANET) is dynamic, can be quickly configured, and lacks features such as wireless APs and adapters. Due to these benefits, a MANET system is able to be applied to specific situations, such as search and rescue operations, military use or emergency operations. Based on the routing protocol, node connections provide information to each other and can jointly establish a complete transmission path independently. But security is a major issue in MANET systems. Because MANET system are open and perform on a non-centralized infrastructure, they lacks security considerations in routing protocols, which make MANET systems more difficult to secure than wired networks. Attacks are easily exploited by its weaknesses.
    In this study, we conducted further research on the most common Sybil Attack of MANET systems. The common Sybil attack may cause packet flow redirection and other extended effects. We used the simulation environment NS-3 Project to create a consensus-based practical Byzantine Fault Tolerance algorithm to explore solutions to the Sybil attack's threat to free mobile networks. Ensuring that all the original network nodes that are vulnerable to tampering are protected can ensure the integrity of the data during transmission. We must demonstrate in the simulation experiment that this method can have an ideal performance in both network and security performance. The goal is to ensure that the general network has the security of the network form under the infrastructure without being compromised.

目錄
第一章、	緒論...........................................1
1-1研究背景與動機.......................................1
1-2研究目的.............................................4
1-3論文的組織與架構......................................5
第二章、	文獻探討........................................6
2-1無線隨意網路..........................................6
2-2隨意行動網路安全......................................7
2-2-1安全服務...........................................8
2-2-2網路攻擊...........................................9
2-3女巫攻擊...........................................11
2-3-1攻擊方法.........................................12
2-3-2攻擊型態.........................................13
2-4拜占庭將軍問題......................................14
2-4-1口頭消息OM(M) ...................................15
2-4-2簽名消息SM(M) ...................................18
第三章、	研究方法與步驟................................21
3-1 PBFT算法流程.....................................24
3-1-1預準備(pre-prepare) ............................25
3-1-2準備(prepare) ..................................26
3-1-3確認(commit) ...................................27
第四章、	實驗及結果....................................29
4-1NS3模擬...........................................29
4-2Sybil節點的攻擊方式................................30
4-3防禦機制..........................................31
4-4節點吞吐量比較.....................................32
4-5多個惡意節點實驗...................................33
第五章、	結論..........................................36
參考文獻...............................................37
附錄-英文論文..........................................40

圖目錄
圖一 女巫攻擊的攻擊方法、類型、時間......................12
圖二 女巫攻擊的網路型態.................................13
圖三 OM(1)算法圖.......................................18
圖四 SM(1)算法圖......................................20
圖五 PBFT流程圖.......................................24
圖六 PBFT算法節點的執行流程圖..........................25
圖七 節點模擬設置......................................29
圖八 模擬女巫攻擊.....................................30
圖九 Sybil節點成功串改消息.............................31
圖十 防禦及偵測惡意攻擊.................................32
圖十一 女巫攻擊的吞吐量.................................32
圖十二 使用PBFT機制的吞吐量............................33
圖十三 25個惡意節點存在網路模擬........................34
圖十四 25個惡意節點存在網路模擬........................34
圖十五 惡意節點攻擊成功竄改網路訊息.....................35

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