臺灣博碩士論文加值系統

當使用者設備的計算能力不足時，除了升級硬體設備之外，也可以選擇使用雲端計算服務，將複雜的運算委外給雲端服務器計算。而在密碼學中，指數運算是經常被用到但卻是成本昂貴的技術之一。
委外運算技術要點可以側重在正確性以及安全性，其中正確性是指計算結果是否正確，雲端服務器可能因為執行錯誤的運算演算法、感染惡意程式或者是其他的情況而不小心或惡意回傳錯誤的計算結果。由於真實的計算結果在委外運算時被隱匿，縱使雲端服務器是不可信任的，將一些涉及秘密的運算委外交由雲端來計算仍舊不會洩漏任何的機密資訊。
本研究將會提出兩種可驗證的委外演算法，分別為固定指數以及固定底數的兩種批次指數運算。我們的方法中，指數運算可以委外給可能是不可靠或有惡意的雲端服務器。此外，提出的演算法也將應用於密文策略基於屬性的加密系統。我們設計了一個具檢查機制的委外加密運算，並將其應用於物聯網的環境架構中。

When the computing ability of the user equipment is insufficient, apart from upgrading hardware devices, cloud computing services may adopt the outsourcing of complex operations to the cloud server. In cryptography, the exponential calculation is one of basic and often used operations, but has expensive computational cost.
Outsourcing techniques can focus on correctness and security. Correctness refers to whether the calculation results are correct. The cloud server may carelessly or maliciously return incorrect computation share results due to executing wrong computational algorithm, being infected with malware, or suffering from other situations. Since the actual computation results are concealed during outsourcing, even if the cloud server cannot be trustworthy, the outsourcing of secret-related operations to the cloud will still not leak any secret information.
This thesis proposes two kinds of verifiable outsourcing algorithms, fixed base-variable exponent and fixed exponent-variable base batch exponentiations. The exponential operations can be outsourced to the cloud servers, which may be untrusted or malicious. In addition, the proposed algorithms will be applied on Ciphertext Policy Attribute-based Encryption (CP-ABE). We design a new outsourced encryption algorithm with checkability and also propose its application on a secure communication protocol under the environment of Internet of Things (IoT).

摘要 i
Abstract ii
致謝 iv
CONTENTS v
LIST OF FIGURES viii
LIST OF TABLES ix
Chapter 1. Introduction 1
1.1 Overview 1
1.2 Motivation 1
1.3 Contribution 2
1.4 Organization 2
Chapter 2. Related Work 3
2.1 Batch Exponentiations Outsourcing with Fixed Base-variable Exponent 3
2.2 Batch Exponentiations Outsourcing with Fixed Exponent-variable Base 4
Chapter 3. High-Performance Batch Exponentiation Outsourcing with Checkability 5
3.1 Security Degree Parameter 5
3.2 Distribution Algorithm 6
Chapter 4. Efficient Ciphertext Policy Attribute-Based Encryption through Outsourcing with Checkability for the Internet of Things 8
4.1 Preliminaries 9
4.1.1 Bilinear Maps 9
4.1.2 CP-ABE Model 9
4.1.3 Outsourcing the Decryption of CP-ABE 10
4.1.4 Cooperative Ciphertext Policy Attribute-based Encryption for the Internet of Things (C-CP-ABE) 11
4.2 Network Model and Security Assumption of Proposed Scheme 12
4.2.1 Network Model 12
4.2.2 Assumption 13
4.3 Proposed Scheme 13
4.4 Construction Detail 14
4.4.1 Split Algorithm 17
4.4.2 PickOut Algorithm 19
4.4.3 CheckResult Algorithm 20
Chapter 5. Experiment 22
5.1 Experiment Tools and Environment 22
5.2 Experimentation Framework 23
5.3 Experimentation Detail: Demo.java 24
5.4 Implementation Structure 25
Chapter 6. Security and Performance Analysis 26
6.1 Security analysis 26
6.1.1 Security Degree 30
6.1.2 Computational Accuracy 30
6.2 Performance Analysis 30
6.2.1 Computation cost 30
6.2.2 Communication cost 30
Chapter 7. Conclusion and future works 31
References 32

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[2] J. Bethencourt, A. Sahai, and B. Waters, “Ciphertext-policy attribute-based encryption,” 2007 IEEE Symposium on Security and Privacy (SP'07), IEEE Press, pp. 321-334, 2007.

[3] V. Goyal, O. Pandey, A. Sahai, and B. Waters. “Attribute-based encryption for fine-grained access control of encrypted data,” In Proc. the 13th ACM conference on Computer and communications security, ACM, pp. 89-98, 2006.

[4] M. Green, S. Hohenberger, and B. Waters. “Outsourcing the decryption of ABE ciphertexts,” in Proc. the 20th USENIX conference on Security, pp. 34-34, 2011.

[5] X. Ma, J. Li, and F. Zhang, “Efficient and secure batch exponentiations outsourcing in cloud computing,” 2012 4th International Conference on Intelligent Networking and Collaborative Systems (INCoS), IEEE Press, pp. 600-605, 2012.

[6] L. Touati, Y. Challal, and A. Bouabdallah, “C-CP-ABE: Cooperative ciphertext policy attribute-based encryption for the Internet of Things,” 2014 International Conference on Advanced Networking Distributed Systems and Applications (INDS), IEEE Press, pp. 1-6, 2014.

[7] J. Wang, “Java Realization for Ciphertext-Policy Attribute-Based Encryption,” https://github.com/junwei-wang/cpabe/, 2012.

[8] B. Waters, “Ciphertext-policy attribute-Based encryption: An expressive, efficient, and provably secure realization,” Public Key Cryptography, vol. 6571, pp. 53-70, 2011.