雲端儲存可以讓使用者輕易的儲存資料，但儲存在雲端伺服器的外包資料其正確性是否有被確保則是個問題，由於使用者將資料儲存到雲端後本地端的原始資料就會刪除，因此檢查這些外包資料的正確性將會是個困難的任務，因此我們需要一個高效且能夠達成公共稽核的第三方(Third-party Auditor ,TPA)來完成檢查正確性的任務，但TPA做為一個第三方，我們並不能完全信任它，我們希望TPA能夠稽核資料的正確性，同時在稽核過程中不能得知有關使用者的資料內容，因此如何設計稽核流程成為這個議題的關鍵。
    在第三方稽核方案的議題中，我們需要考量的幾個要點有:方案運算時間、支持批次稽核、隱私性;過去所提出的方案裡，已有完整的第三方公開稽核流程，但其隱私性是有洩漏的可能性，雖然在近年的方案中，有人提出以遮蔽的方式來解決隱私性的問題，但我們發現這樣的方式依然存在著資料被解讀的可能性，因此我們將以過去的方案為基礎，並加以改良來補足其隱私性的缺陷。 
    我們以過去的方案為基本架構，並對稽核的流程做改良，透過這樣的改動，解決了過去隱私性洩漏的問題;此外我們針對無效回應的問題做出改良，使TPA在進行批次稽核時，即便有無效的回應，也不會使其運算時間上升。
    我們在文中證明了TPA如何針對過去方案來破解使用者的資料，並且在同樣的攻擊模式下是無法由我們所提出的方案達到相同的目的;此外我們利用Pairing-Based Cryptography(PBC)函式庫來模擬過去方案以及我們提出的方案，並進行各種情況下的模擬，最後可看出我們所提出的方案在增進隱私性的同時，不會使得使用者、雲端伺服器、TPA這三個實體增加額外的運算時間。

Cloud storage allows users to store data easily, but whether the integrity of outsourced data stored in the cloud server is guaranteed that is a problem. Because the local data will be deleted after the user saves data to the cloud, checking the integrity of the outsourcing data will be a difficult task. We need a efficient third-party which is able to support public audit (Third-party Auditor, TPA) to complete the task of checking the data integrity, but TPA as a third party, which we can not trust it completely. We hope that TPA can audit the integrity of the data, and TPA can not learned about the user's data in the audit processes,  so how to design the audit processes become the key issue.
In the issue of third-party audit strateties, we need to consider few key points: the strategy computation time, supporting batch audit, and privacy protection. The proposed strategies in the past have been complete third-party audit processes, but there is the possibility of privacy leakage. Although a strategy has been proposed which blinds the parameter to solve the privacy problem in recent years, we find it still exists the possibility of data to be learned. So we will enhance the privacy protection based on past strategies. We improve the audit processes to solve the problem of privacy leakage. In addition we make improvements for the problem of invalid responses. When TPA does the batch audit, even if there exists invalid responses, it does not increase computation time.
We show how the TPA learn user's data in past strategies in this paper, and in the same attack patterns TPA can not achieve the same purpose in the strategy we proposed. In addition we use Pairing-Based Cryptography (PBC) library to simulate our strategy and the strategies which are proposed in the past under the variety of situations. Finally, we can see that our strategy improves the privacy protection, at the same time doesn't increase the computation time of the three entities, the user, the server, and the TPA.

目錄
第一章、緒論	1
1.1、研究動機	1
1.2、問題描述與解決方案	2
1.3、論文架構	3
第二章、相關研究背景	4
2.1、背景知識	4
2.1.1、第三方稽核架構	4
2.1.2、橢圓曲線密碼學	6
2.1.3、雙線性映射函數	7
2.2、過去的解決方案	8
2.2.1、PoR	10
2.2.2、Blind方案	14
第三章、提出之新方案	18
3.1、設計概念	18
3.2、方案流程	19
3.2.1、新方案之基本稽核流程	19
3.2.2、新方案之批次稽核流程	20
3.2.3、新方案評估	22
第四章、模擬與效能評估	23
4.1、隱私成效評估:Zero Knowledge Proof	23
4.1.1、PoR	23
4.1.2、Blind	26
4.1.3、新方案	29
4.2、運算時間評估	31
4.2.1、User運算時間	32
4.2.2、Server運算時間	34
4.2.3、Batch運算時間	35
4.2.4、無效回應運算時間	42
第五章、結論與未來展望	50
5.1、結論	50
5.2、未來展望	52
附錄	53
參考文獻	54

 
圖目錄

圖2.1、第三方稽核架構圖	4
圖2.2、第三方稽核流程簡圖	8
圖4.1、User運算時間比較圖	32
圖4.2、Server運算時間比較圖	34
圖4.3、PoR的單次與批次稽核時間比較圖	36
圖4.4、Blind的單次與批次稽核時間比較圖	36
圖4.5、Ours的單次與批次稽核時間比較圖	37
圖4.6、各方案單次稽核時間比較圖(c=300)	38
圖4.7、各方案批次稽核時間比較圖(c=300)	39
圖4.8、各方案單次稽核時間比較圖(c=460)	39
圖4.9、各方案批次稽核時間比較圖(c=460)	40
圖4.10、二元搜尋運算流程圖	43
圖4.11、PoR的無效回應稽核時間比較圖	45
圖4.12、Blind的無效回應稽核時間比較圖	46
圖4.13、Ours的無效回應稽核時間比較圖	46
圖4.14、各方案無效回應單次稽核時間比較圖(c=300)	47
圖4.15、各方案無效回應批次稽核時間比較圖(c=300)	48
圖4.16、各方案無效回應單次稽核時間比較圖(c=460)	48
圖4.17、各方案無效回應批次稽核時間比較圖(c=460)	49

 
表目錄
表2.1、ECC與RSA密鑰長度	6

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