近年來,隨著世代的改變,雲端的發展也逐日漸進,很多家公司開始提供雲端空間的服務，像是Google Drive , Dropbox, Box......等。由於這些雲端空間服務程式都會有自己的應用程式，若我們有很多不同的雲端空間服務的帳號，就要安裝來自不同提供商給的應用程式;若我們沒有使用專屬的應用程式，自然無法連結到我們的檔案。現今，很多人擁有不同的雲端帳號，但電腦一次卻只能執行一個帳號、雲端空間的限制也是另許多使用者煩惱的問題。
而存在雲端的資料，大家最為關心的就是安全性的考量，雖然各個雲端服務提供商都宣稱自己有做加密的保護且不會去看使用者的檔案，但相信很多用戶還是會擔心安全性及私密性的問題，畢竟檔案都在雲端空間上。
為了解決以上的問題，我們提供一個可以整合多個雲端儲存空間的架構，透過我們的架構，使用者可以容易的管理不同雲端空間資料且不需要下載來自不同雲端提供商所給的程式．為了突破免費容量的限制，我們讓用戶可以把許多免費空間串接起來。另外，我們也考量了安全性的問題，提供加密及解密的服務，讓使用者保有檔案的鑰匙，只有自己才可以解鎖。

In recent years, due to rapid advancement in network and computer technologies, cloud services have been gradually developed. Among all cloud services, online storage or cloud storage attracts a lot of attention. Many companies, such as Dropbox, Google and etc. have started offering cloud storage services. Being able to access our data from anywhere and at any time, the convenience offered by cloud storage services has fundamentally changed our daily lives.
However, the cloud storage services offered by commercial companies in their current form have two drawbacks. First, to use the cloud storage service conveniently offered by a specific cloud storage service provider, users have to install a synchronization program offered by the service provider in their local hosts. This synchronization program keeps the files in the local host synchronized with their remote copies in the cloud. The synchronization programs inevitably allow only one cloud storage service account in each local host. This limits the storage space that users can use. The second drawback of the current cloud storage services is security concern. Although all companies offering cloud storage services claim that users' files are securely encrypted and that maintaining users' privacy has the top priority, most users still worry since the companies also hold the decryption keys.
In this thesis we present an architecture to address the two drawbacks described above. In our architecture locally files are maintained in a file tree and remotely our architecture distributes files in multiple cloud storage accounts, such that no account violates its space limit. In our architecture files are encrypted before they are stored in cloud storage accounts. Only users have the decryption keys. In this thesis we also present a prototype implementation of the architecture.

Contents 1
List of Tables 3
List of Figures 4
1 Introduction 5
2 Survey Service 7
2.1 MultCloud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Boxcryptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3 Architecture Block 9
3.1 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2 Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4 Application Implementation 12
4.1 Communication Header . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2 Rsync Alogorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.3 File Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3.1 Local Database . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3.2 File created event . . . . . . . . . . . . . . . . . . . . . . . . 17
4.3.3 File deleted Event . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.4 File Renamed Event . . . . . . . . . . . . . . . . . . . . . . 19
4.3.5 File Modified Event . . . . . . . . . . . . . . . . . . . . . . 20
4.4 Other Devices Synchronization . . . . . . . . . . . . . . . . . . . . 22
4.4.1 Other Devices Created Event . . . . . . . . . . . . . . . . . 22
4.4.2 Other Devices Renamed Event . . . . . . . . . . . . . . . . 24
4.4.3 Other Devices Deleted Event . . . . . . . . . . . . . . . . . 24
4.4.4 Other Devices Modified Event . . . . . . . . . . . . . . . . . 24
4.5 File Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.5.1 Renamed Event . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.5.2 Modified Event . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.6 Initial Application and Cloud Storage . . . . . . . . . . . . . . . . . 28
4.6.1 Initial Application . . . . . . . . . . . . . . . . . . . . . . . 28
4.6.2 Initial Cloud Storage . . . . . . . . . . . . . . . . . . . . . . 30
4.7 Redistribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.8 Update Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.9 Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.9.1 Files Encryption and Decryption . . . . . . . . . . . . . . . 34
4.10 Icon Overlay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5 Install Tool 38
5.1 Launch4j . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.2 Nullsoft Scriptable Install System . . . . . . . . . . . . . . . . . . . 38
6 Application Interfere 40
6.1 Register and Login Interface . . . . . . . . . . . . . . . . . . . . . . 40
6.2 Importing multiple accounts . . . . . . . . . . . . . . . . . . . . . . 41
6.3 File encryption and fixed short cut Interface . . . . . . . . . . . . . 42
7 Future Work 43
8 Conclusion 44
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

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