隨著行動裝置的盛行與追求更高服務品質的目標，國際間的學者與企業逐漸開
始關注下個行動網路世代的發展走向。第五世代(5G) 行動通訊網路可說是一套不同於現今網路，具彈性、高效能且可靠的新形態網路架構，並預計於2020年問世。為了建構一個具高效能且安全的行動網路，已經有些明確的技術趨勢被發表。
在本篇論文中，我們將集中探討其中一項關於基礎設施的5G技術趨勢，即小型
基地台(small cells) 的發展與佈建。發送訊號的基地台將被設計成不同型號大小，小型基地台有各自不同的涵蓋範圍，並將被大量佈署於5G行動網路當中。如此的策略能幫助我們節省大量的能源消耗，還能夠加強行動通訊網路的涵蓋範圍，此外，通道容量也會隨著小型基地台佈建的數量而有顯著的提升。然而，我們發現這樣的未來趨勢與目前4G所使用的換手(handover) 機制有些相抵觸的地方。因為大量小型基地台的佈建而使得使用者執行換手的頻率增加。假設5G沿用4G的換手機制，亦即使用者必須在每次換手時與最大的基地台(macro cell) 聯絡，則整體的延遲時間將隨著換手次數而大幅成長。為解決此問題，我們將提出一套針對5G環境設計的快速換手認證機制，並提出對應的安全證明與分析，此外，我們的機制還符合了隱私保護、低運算成本和主動性撤銷的特性。

Due to the rising number of mobile devices and the increasing demand for better quality of service (QoS), issues related to the next generation of mobile networks are gaining significant attention from academia and business on the global level. One such network, known as the fifth generation (5G) mobile communication network, could provide a flexible, reliable, and high-performance network architecture for wireless communication beyond 2020. 5G combines many types of technologies, including radio access technologies (RATs), hardware improvements, and algorithms.
In order to build such a high-performance mobile communication network with robust security, many technical solutions have been proposed. One such solution, known as small cells, deploys large numbers of base stations of different sizes within the service scope of the wireless networks. By deploying small cells, we can improve the power utilization, channel capacity, and coverage of 5G. However, changes in infrastructure between 4G and 5G may cause another problem.
Assume that 5G inherits the connection principle of 4G, in which a user terminal must connect to macro cells, the largest base stations, whenever it runs the handover protocol. The number of handovers executed by the user terminals will increase substantially owing to the large number of small cells, thus increasing the total latency. Therefore, we want to construct a handover authentication protocol that is secure, cost efficient, and tailored to 5G. This protocol will also preserve privacy and provide a functional active revocation mechanism that can revoke warrants in emergencies.

論文審定書i
Acknowledgments iv
摘要v
Abstract vi
List of Figures ix
List of Tables x
Chapter 1 Introduction 1
Chapter 2 Preliminaries 4
2.1 Fifth Generation (5G) Mobile Networks . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3 Handover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4 Digital Signature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.5 One-Way Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.5.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.5.2 Nyberg’s Fast One-Way Accumulator . . . . . . . . . . . . . . . . . . . 12
2.6 Security Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Chapter 3 Related Works 20
3.1 Jing et al.’s Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2 Fu et al.’s Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.3 He et al.’s Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Chapter 4 The Proposed Scheme 30
4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.2 The Proposed Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Chapter 5 Security Proof and Properties Analysis 40
5.1 Security and Properties Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.2 Security Models and Proofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.3 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Chapter 6 Conclusion 52
Bibliography 53

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