當檔案系統執行支援安全資料刪除的格式化時，就是為了確保被格式化的檔案無法使用任何方法再度讀取出來。隨著資源受限之快閃記憶體裝置的儲存空間越來越大，安全資料刪除所花的時間也慢慢成為一個重要的問題。比起現有的安全資料刪除方法(花大量的時間把所有檔案內容重寫)，我們提供了一種有效率的安全刪除機制，一種不需要把所以檔案資料重寫的安全刪除，因此可以節省大量的時間，而且適用於各種類型的檔案系統跟各種儲存規格的裝置。我們採用真實的工作負載進行了一連串的實驗來檢驗我們的機制，結果顯示，在大部分的情況下，我們僅僅花微小的代價就可以達到安全資料刪除。

The support of secure deletion on formatting a file system is to make sure that when a file system is formatted, there is no way to get any file content back again. Due to the fast-growing storage capacity, the performance of secure deletion to file systems on resource-constrained flash storage devices has become a critical issue. In contrast to the existing works that take a long time on overwriting/resetting all the file contents of a file system, we propose an efficient secure deletion scheme to securely delete all the contents of a file system without rewriting file contents. Thus, secure deletion to file systems can be efficiently achieved and can be independent of the device capacity and file systems. A series of experiments was conducted with realistic workloads to evaluate the capability of the proposed scheme. The results show that the proposed scheme achieves secure deletion with limited performance overheads in most cases.

摘要 iii
Abstract iv
Chapter 1. Introduction 1
Chapter 2. Background and Motivation 6
2.1 Background 6
2.2 Motivation 14
Chapter 3. An Efficient Secure Deletion Scheme 17
3.1 Overview 17
3.2 SDS: A Secure Deletion Scheme 19
3.3 SDS+: A SDS with Reduced RAM Space 22
3.3.1 Design Principles of SDS+ 22
3.3.2 Running Examples of SDS+ 30
Chapter 4. Analysis of Data Security 34
Chapter 5. Performance Evaluation 35
Chapter 6. Conclusion 42
References 44

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