Vehicular Ad hoc Networks have become more important topic in recent years. The development of Vehicle to Vehicle communication (V2V) and Vehicle to Infrastructure communication (V2I) provide many applications and services. Location verification is one of the crucial issues for VANETs, since forged position information has severe impact regarding both security and safety. In order to resist this problem, we propose a detection mechanism that is capable of recognizing nodes cheating about their position. The main idea of our proposed scheme is that with the help of reliable neighbors, each vehicle can deduce where a vehicle is currently driving. The analysis and evaluation of our protocol justify that our protocol has better performance on enhancing VANET security.

近年來隨著車用電子網路的發展與應用越來越蓬勃，無論是車體對車體之間的無線傳輸；亦或，車體和路面基礎建設的通訊，皆使得智慧運輸系統上的安全模式、交通便利性和商業應用上有廣泛的效益。然而，網路所帶來的便利性卻蘊含著潛在的危機，網路上的惡意攻擊層出不窮，使用這些應用服務的前提之下，必須滿足安全性的需求。如何增進行車時的道路交通安全並避免任何可能發生的交通事故更成為未來首要達成的目標。
此篇論文的研究主要是在車用無線隨意網路中發展一個可以認證節點相對位置並有效偵測出惡意節點於封包中偽造位置的機制，利用預測區域的概念，使得驗證車輛能夠根據來源封包內所紀錄的時間進而計算得到來源車輛的相對位置，並藉由鄰近車輛所計算出之結果做重疊比對以提升駕駛人的行車經驗及降低事故發生率。

Table of contents .........................................I
List of Figures..........................................III
List of Tables ...........................................IV
Chapter 1 Introduction ....................................1
Chapter 2 Related Works ...................................4
2.1 Convoy Member Authentication (CMA).................... 5
2.2 Vehicle Sequence Authentication (VSA) ................ 7
Chapter 3 Proposed Scheme................................ 11
3.1 Assumptions.......................................... 11
3.2 Attacker Model....................................... 12
3.3 Zoned-based Vehicle Location Authentication (ZVLA) .. 13
Chapter 4 Analysis....................................... 23
4.1 The Attacks on ZVLA.................................. 23
4.2 The Security Analysis of ZVLA ....................... 24
4.3 Overhead Analysis on ZVLA............................ 33
Chapter 5 Simulation .................................... 34
5.1 Simulation Settings ................................. 34
5.2 The Pattern of Attackers............................. 34
5.3 Simulation Results................................... 35
5.3.1 The Impact of the Amount of Adversary.............. 36
5.3.2 The Impact of Vehicle Density...................... 39
Chapter 6 Conclusion and Future works ................... 41
Bibliography ............................................ 44
Appendix ................................................ 44

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