隨著工業4.0的蓬勃發展，為了能夠提升作業效率、改善產品品質與降低成本的考量，近年來製造業接二連三地從傳統製造轉型為智慧製造，將網路實體系統(Cyber-Physical System, CPS)導入工業控制系統(Industrial Control System)，藉由CPS的資訊技術(IT)和操作技術(OT)來做到即時監控、互操作性和虛擬化等功能。然而，除了享受CPS所帶來的便利與利益，其潛在威脅和漏洞也帶入了工業控制系統，因為CPS的特性導致工業控制系統與外部網路或系統之間隔絕的程度愈來愈低，使其所面臨的網路安全風險迅速升高，如竊聽、竄改與病毒感染等攻擊。因此我們設計出了一種基於線性反饋移位暫存器之加密機制，透過動態產生對稱式金鑰來加密每一筆資料，以保護工業控制系統內部資料傳輸過程。經由模擬實驗結果，所提出的加密機制每秒約可加密2 MB大小的資料，因此能夠適用於工業控制系統的硬體設備。除此之外，我們針對提出的加密機制進行安全性分析，提出的加密機制是可防止駭客竊聽以及中間人攻擊。

With the rapid growth of Industry 4.0, the manufacturing industries apply cyber-physical systems (CPS) to their industrial control system (ICS) to improve the efficiency of operations, product quality and reduce costs. By the information technology and operational technology of CPS to achieve real-time monitoring, interoperability, and virtualization. However, unless the convenience and benefits of CPS, the characteristics of CPS lead to the isolation between the industrial control system and the external network or system be getting lower and lower, so the vulnerabilities and attacks are rising rapidly. Therefore, we propose a symmetric encryption scheme based on a linear feedback shift register to encrypt each data by dynamically generating the symmetric key to protect the internal data transmission of the industrial control system. Through the simulation result, the proposed encryption scheme could encrypt 2MB per second approximately so it is capable to execute on device and equipment of industrial control systems. Furthermore, we do the security analysis against the proposed encryption scheme, it could prevent hacker eavesdropping and man-in-the-middle attacks.

中文摘要 i
Abstract ii
誌謝 iii
Contents iv
List of Figures vi
List of Tables vii
Chapter 1 Introduction 8
Chapter 2 Literature Reviews 14
2.1 Symmetric Encryption Algorithm 14
2.1.1 Block Cipher 15
2.1.2 Stream Cipher 15
2.1.3 Existing Symmetric Encryption Algorithms 15
2.2 Linear Feedback Shift Register 17
2.3 Linear Congruential Generator 19
2.4 Discussion 20
Chapter 3 The Proposed Encryption Scheme 22
3.1 System Model 22
3.2 The Encryption Scheme 23
3.2.1 Assumptions 24
3.2.2 Data Encryption 25
3.2.3 Data Decryption 27
Chapter 4 Performance Analysis 29
4.1 Simulation Environment 29
4.2 Simulation Examples 30
4.3 Performance Analysis 30
Chapter 5 Security Analysis 37
5.1 Eavesdropping 37
5.2 Man-in-the-middle Attack 38
Chapter 6 Conclusion 39
Reference 40

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