But what Google can’t see they can’t use right? :-)
Using EncFS and some tools you can create a totally secure encrypted filesystem on top of the standard Google Drive in under 5 minutes.
Mac OS instructions only below.
First download and install Fuse4X and a version of EncFS which uses the Fuse4X APIs. Thanks to Simone Lehmann for providing an EncFS Mac installer at http://www.lisanet.de/?p=128 (also mirrored here).
To create a new encrypted volume (stored locally at first to prevent the EncFS key from being synchronised with Google Drive):
encfs ~/Desktop/_Encrypted ~/Documents/_GSecure
Answer ‘yes’ when prompted to create the new folders and choose ‘p’ for pre-configured paranoia mode (256-bit AES encryption). Enter a secure EncFS password when prompted and you’re done.
Now the filesystem has been created we can deal with securing the key.
mv ~/Desktop/_Encrypted/.encfs6.xml ~/.keys/gsecure.xml
The commands above move your key from the EncFS filesystem into a hidden folder in your (local) home directory
Now move the entire
~/Desktop/_Encrypted folder (minus your key) into your Google Drive:
mv ~/Desktop/_Encrypted ~/Google\ Drive/
Finally download my GSecure application and copy it to your Applications folder.
The first time you run GSecure it will prompt you for your EncFS password which it stores in your local login keychain. The password must match the secure password you set in a previous step.
To mount or unmount the encrypted filesystem simply run the GSecure app. For convenience copy it to your Mac OS Dock for quick access.