近年來，由於無線通信技術的迅速發展以及該技術在遠程信息處理中的應用，車載隨意行動網路(Vehicular Ad-Hoc Network)的部署已經逐漸開始。在過去的幾年中，車輛通信研究中最引人入勝的問題之一是車輛通信中應將多少重點放在匿名信息上的問題。

本論文提出了一個多層次的車載隨意行動網路的框架，以確保車輛條件匿名性和可追溯性。該框架是一個多層次的體系結構，包括裝載車載單元的車輛，路邊單元，Local Trust Authority（Edge Server），Registration Authority（Cloud Server）和Trust Authority（Cloud Server）。除此之外，我們提出了分區的概念，並在每個區域之中設置區域管理員Local Trust Authority，他和路邊單元是位於這些不同區域的分佈式節點，並將群簽章機制應用在這種體系結構中進行匿名驗證以實現條件匿名以及可追蹤性。基於比特幣相關分層確定性錢包的啟發，每一台車輛能夠根據自身的種子產生一個假名樹，只有再需要用到特定編號的假名時才需要依需求產生車輛假名。在本論文的最後，我們亦有實作實驗來驗證我們所提出的框架及協定，並且對其進行安全性分析，以證明此框架能同時兼具效率與安全。

In recent years, due to the rapid development of wireless communication technology and the application of this technology in telematics, the deployment of the Vehicular Ad-Hoc Network has gradually begun. In the past few years, one of the most fascinating issues in vehicle communication research is how much emphasis should be placed on anonymous information in vehicle communication.

This thesis proposes a multi-level Vehicular Ad-Hoc Network framework to ensure the conditional anonymity and traceability of vehicle. The framework is a multi-layered architecture, including vehicles loaded with On-Board Units, Roadside Units, Local Trust Authority (Edge Server), Registration Authority (Cloud Server) and Trust Authority (Cloud Server). In addition, we proposed the concept of region and set up a Local Trust Authority in each region as a region manager. Local Trust Authority and the Roadside Unit are distributed nodes located in these different areas, and the group signature mechanism is adopted to provide anonymous authentication for achieving conditional anonymity and traceability. Subsequently, based on the inspiration of Bitcoin-related Hierarchical Deterministic Wallets, each vehicle can generate a pseudonym tree based on its own seed, and only when a specific pseudonym is needed, the vehicle will generate it. Furthermore, we conducted simulation and security analysis to prove the framework we proposed can achieve efficiency while safety concerns are also included.

Table of Contents
摘要 I
Abstract II
Acknowledgement III
Table of Contents IV
List of Figures VI
List of Tables VII
Chapter 1 Introduction 1
Chapter 2 Preliminaries 7
2.1 Group Signature 7
2.2 Hierarchical Deterministic Wallet 9
2.3 Elliptic Curve Diffie-Hellman Ephemeral 10
Chapter 3 Literature Review 12
3.1 PKI-oriented Scheme 12
3.2 Identity-based Scheme 13
3.3 Group Signature-based Scheme 14
3.4 Symmetric Cryptography-based Scheme 16
3.5 Mix-zone-based Scheme 16
Chapter 4 Proposed Framework 19
4.1 Framework Scenarios 19
4.2 Assumptions 22
4.3 Protocol Design 22
4.3.1 System Setup 24
4.3.2 Registration Phase 26
4.3.3 Region Joining Phase 27
4.3.4 Vehicle Disclosure Phase 33
Chapter 5 Experiment and Analysis 39
5.1 Experiment Environment and Result 39
5.2 Security Analysis 41
Chapter 6 Conclusion and Future Work 45

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