利用備份與投票技術實作雲端儲存之即時行為違反證明技術

Abstract

這篇論文中我們研究如何開發一個有效率的即時稽核技術以及雲端儲存系統使用的違反證明技術 (Proof of Violation；簡稱 POV)。POV 技術可以讓使用者或是服務提供者做出密碼學的證據，可以用來證明服務提供者違反特性 (Properties)，或讓服務提供者證明自己的清白。POV 技術是讓雲端的使用者和服務提供者擁有互相不可否認性的技術。即時的稽核會在每一次的檔案操作之後執行，以確保可以即時發現服務提供者的違反行為。在目前所知的解決方法中，他必須要在客戶端的裝置中保留檔案的雜湊值，客戶端儲存及同步這些檔案的雜湊值會照成極大的負擔，而且當一個客戶端一段時間未做檔案操作，下一次檔案操作前的同步動作會花上非常長的時間。 我們提出一個投票的方法讓客戶端的設備不需要保留任何的檔案的雜湊值。利用多個獨立的服務提供者，客戶端不僅能即時的稽核、支援 POV 技術，又能同時擁有多份的備份。實驗結果顯示，本論文提出的方法相較於之前的雲端儲存即時稽核技術，平均來看能夠節省8倍的時間，遇到最糟的情況能夠節省超過20倍的時間。雲端儲存的服務提供者可以利用我們所提出的方法，將互相不可否認性的保證加入他們的服務層級協議。

In this paper we study how to develop an efficient real-time auditing and proof of violation on cloud storage. Proof of violation can let user and service provider generate cryptographic proofs that used to proof service provider’s properties violate, or let service provider proof it’s innocence. Proof of violation are solutions for obtain mutual nonrepudiation between user and service provider. Real-time auditing perform on the end of every file operation so that the violation of the service provider can be found instantly. Existing solutions need to cache file’s hash value on client device. Storing and synchronize these file’s hash value are really huge overhead for client device. If a client device being offline in ages, synchronize to latest file’s hash value will speed a really long time. We propose a real-time proof of violation for cloud storage by replication and voting that let client device don’t need to cache any file’s hash value. Using multiple Independent service provider so that client device can real-time audit, support proof of violation, and having multiple file replication. Experimental results are presented that our scheme outperforms previous work 8 times by average, and in the worst case our scheme outperforms previous work by 20 times. Service providers of cloud storage can use the propose scheme to provide a mutual nonrepudiation guarantee in their service-level agreements.