A Study on Data Deduplication and Data Sharing in Cloud Storage Service

鑒於目前雲端儲存服務的普及，越來越多人或組織將資料放上雲端儲存做備份或與他人共享，例如：Google Drive, Dropbox。從雲端服務供應商的角度來看，若能以最精簡的空間達到最大的儲存效果，是最佳的儲存方式。雖然雲端儲存服務提供使用者在檔案的備份及分享上能更彈性也更便利，但在分享的同時，雲端儲存中資料的隱私性及安全性仍受到許多的質疑，也是許多使用者所關心的問題。 因此，本研究於第三章提出了一個能有效地檢查資料重複性同時檢驗資料完整性的資料重覆刪除(data deduplication)技術。此外也於本研究第四章及第五章提出了兩個雲端資料分享的方法以達到資料分享的隱私性及安全性，這兩個方法皆符合前推安全與後推安全，資料來源驗證，資料完整性及資料機密性等四個雲端儲存服務應具備的安全需求。最後，我們也將所提出的兩個資料分享機制與其他學者提出的資料分享架構作安全性與計算成本的分析比較，以衡量各方法之成效。The populace of data sharing through cloud service, such as Google Drive and Dropbox, has increased these days. In the aspect of cloud storage service provider, it is the best solution if they can store the most data in the least capacity. Though the cloud storage service provides more flexibility and convenience on data sharing, it is much concerned for the issues of privacy and security while the data is shared. In this study, an efficient data deduplication scheme is proposed to examine redundancy and integrity of data in Chapter 3. Moreover, two data sharing schemes are proposed in Chapter 4 and Chapter 5 to achieve privacy and security of shared data in cloud storage service. Both of these two schemes satisfy forward secrecy and backward secrecy, source authentication, data integrity, and confidentiality of data. At last, two proposed schemes are compared security requirements and computational cost with other schemes to evaluate the effect of these schemes.誌謝 i 摘要 ii Abstract iii Contents iv List of Tables vi List of Figures vii Chapter 1. Introduction 1 1.1 Motivations 1 1.2 Objectives 3 1.3 Research Scope 4 1.4 Organization 5 Chapter 2. Related Works 6 2.1 Data Deduplication 6 2.1.1 File-Level Deduplication 6 2.1.2 Block-Level Deduplication 6 2.2 View of Zhang’s Fault-Tolerant Digital Signature Scheme 7 2.3 Bilinear Pairing and Some Problems 10 2.4 Message Recovery 11 Chapter 3. Data Deduplication Scheme for Cloud Storage 14 3.1 Preliminary 14 3.2 Proposed Scheme 15 3.2.1 Data Translation Phase 15 3.2.2 Data Deduplication Phase 16 3.3 Discussions 18 3.3.1 The Worst Case Conditions 18 3.3.2 Computational Cost Evaluations 19 3.4 Summary 20 Chapter 4. Data Sharing Scheme for Cloud Storage Service Using Symmetric Cryptosystems 21 4.1 Preliminary 21 4.1.1 Security Requirements 22 4.2 Proposed Scheme 22 4.2.1 The Setup Phase 24 4.2.2 The Initialization Phase 25 4.2.3 The Retrieving Phase 26 4.3 Security Analysis 28 4.3.1 Forward Secrecy and Backward Secrecy 28 4.3.2 Source Authentication 28 4.3.3 Data Integrity 29 4.3.4 Confidentiality 29 4.4 Performance Evaluation 29 4.5 Summary 31 Chapter 5. Data Sharing Scheme for Cloud Storage Service Using the Concept of Message Recovery 32 5.1 Preliminary 32 5.1.1 Security Requirements 33 5.2 Proposed Scheme 34 5.2.1 The Setup Phase 35 5.2.2 The Initialization Phase 36 5.2.3 The Retrieving Phase 38 5.3 Security Analysis 39 5.3.1 Forward Secrecy and Backward Secrecy 39 5.3.2 Source Authentication 40 5.3.3 Data Integrity 40 5.3.4 Confidentiality 41 5.4 Performance Evaluation 41 5.5 Summary 42 Chapter 6. Conclusions and Future Works 43 References 4