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DropVault: View Encrypted DropBox Files on Your iPad

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DropVault is an iPad program that can display files stored in your DropBox account that have been encrypted with a password. The password is never stored in DropBox. Without the password, neither files nor file names can be recovered from your DropBox account.

I wrote this program to “scratch an itch” – I wanted to read confidental documents on my iPad. The easiest way to get documents on my iPad was through DropBox, but I didn’t want to put confidential information on a cloud service.

My solution was to encrypt the documents on my PC before putting them in my DropBox folder. This program would decrypt them on my iPad. It works perfectly for my purposes. However, right now I have no plans to make this program available on the App Store. To be a worthwhile App Store program, it would take a lot more polish around the end-to-end scenario (like desktop programs for Windows and Mac to do encryption). I don’t have time to work on that right now.

However, with the recent interest around DropBox security, I hope this program will be useful to fellow programmers. I’d be thrilled if somebody takes this and turns it into a polished program that makes secure DropBox storage available to the masses.

Interested? Get the source code from GitHub.

How it works

DropVault uses a directory in your DropBox account called StrongBox (yes, that was my earlier name for this project). When you store a file in your StrongBox folder, you decrypt the file with the AES128 algorithm and a randomly generated key. Store the file in the StrongBox folder with a random file name that ends with the extension .dat.

At this point, nobody can read the file in the StrongBox file. Not even yourself! To enable you to read it, create a key file. This file contains the key you used to encrypt the file and the file name, and it is encrypted with a password of your choosing. (Encryption is again done using the AES128 algorithm, using the algorithm from RFC 2898 to derive the encryption key from your password).

Thus, armed with your password, you can recover the file name and decryption key from the .key file.

For Windows machines, I have written PowerShell scripts that automate the encryption process.

On the iPad, this DropVault program automates decryption. It assumes that you use the same password to protect each .key file. You enter your password when you launch DropVault, and from that point on you can read each file just by tapping it.

License

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Notice

  • This project contains code from Google Toolbox for Mac. Google Toolbox for Mac is covered by the Apache 2.0 License.

  • This project contains code from OCMock. This code is covered under the following license:

    Copyright (c) 2004 - 2011 by Mulle Kybernetik. All rights reserved.

    Permission to use, copy, modify and distribute this software and its documentation is hereby granted, provided that both the copyright notice and this permission notice appear in all copies of the software, derivative works or modified versions, and any portions thereof, and that both notices appear in supporting documentation, and that credit is given to Mulle Kybernetik in all documents and publicity pertaining to direct or indirect use of this code or its derivatives.

    THIS IS EXPERIMENTAL SOFTWARE AND IT IS KNOWN TO HAVE BUGS, SOME OF WHICH MAY HAVE SERIOUS CONSEQUENCES. THE COPYRIGHT HOLDER ALLOWS FREE USE OF THIS SOFTWARE IN ITS “AS IS” CONDITION. THE COPYRIGHT HOLDER DISCLAIMS ANY LIABILITY OF ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING DIRECTLY OR INDIRECTLY FROM THE USE OF THIS SOFTWARE OR OF ANY DERIVATIVE WORK.

  • This project uses an icon from Glyphish, which is provided with a Creative Commons attribution license.