Documents in the Cloud
Document editing and managing tools are going online, as evidenced from
Google Docs, Microsoft OfficeLive, and Mozilla Bespin, etc. These
services bring tremendous benefits on document reliability and
usability. However, these benefits come somehow at the cost of
security, since users have to fully trust the cloud service provider
with their data.
There are lots of reasons you might not want to trust the service
provider with your confidential data. Even if you trust them to "not be
evil", their server could have bugs that make it unintentionally reveal
your data (e.g.,
Google
Privacy Blunder Shares Your Docs Without Permission,
TechCrunch, March 2009). A cloud provider could also be subjected to a
subpoena
that requires it to turn over a large amount of information.
Private Documents
We developed an Firefox extension to enable private editing using Google
Documents.
This is a proof-of-concept tool enabling a user to use the cloud editing
service Google Documents securely
(ensuring both data confidentiality and integrity) without totally
trusting the service provider.
Document contents submitted by the user are incrementally encrypted.
Paper
Yan Huang and David Evans. Private Editing Using Untrusted Cloud
Services. Second
International Workshop on Security and Privacy in Cloud
Computing. Minneapolis, Minnesota. 24 June 2011. (PDF, 10 pages)
See also: Encrypted
Google Docs done well, Nate Lawson's commentary on this paper,
Root Labs, 9 May 2011.
Talks
Yan Huang's talk from
Second
International Workshop on Security and Privacy in Cloud
Computing: [
PPTX,
PDF]
Directions
Installing the Extension
Note: the current extension is not compatible with Firefox 4.0.
The code is available here under an open source (MIT) license, but it
will not work with current Firefox releases.
- Download the extension: securedocs.xpi
- Install the addon on Firefox Browser. You can do this by dragging
the file onto your Firefox Browser. The extension has been tested on
Firefox 3.5 and Firefox 3.6. As part of the install process, you will need to restart Firefox.
- On your browser menu, select "Tools -> Secure Google Docs". Now
a check mark appear at this menu item. (Select the item again will disable this add-on.)
- Go to http://docs.google.com, sign in to your google account if necessary.
- Navigate to Google Docs by clicking the "Documents" link.
Creating a new Private Document
- Click the "Create new" button and select "Document".
- A Settings dialog will appear and allow you to set the credentials and encryption schemes to use.
- Click "OK" to confirm your settings; Or click "Cancel" to choose not to use any encryption for this editing session.
Making Existing Documents Private
- Open an existing unencrypted document.
- A Settings dialog should show up. Set the password as you wish, (default is "abc"), and select an appropriate encryption mode. Then click the "Plain Load" button.
- The document loads as normal. Make your edits as usual, but for all subsequent "save"s, Google only sees encrypted messages.
- Close the document after you finish your edits.
Opening Encrypted Documents
- When you want to reopen the document, just make sure you have "Secure Google Docs" add-on enabled and then click to open the
document.
- A similar Settings dialog appears. Enter your password and click the button "Decrypt then Load". Now you get to see your encrypted documents and continue your edits. (If you clicked "Plain Load", or, if you happen to open that document with "Secure Google Docs" add-on disabled, you will see what Google server gets to know. If the password is wrong, the page shouldn't be able to load sucessfully.)
Credits
This extension was developed by Yan Huang in the Security Research Group at the
University of Virginia.
Special thanks to jsCrypto, a fast JavaScript
implementation of AES block cipher we use, developed by Emily Stark,
Mike Hamburg, and Dan Boneh.