While the level of security on Dropbox and other cloud storage services are fine for most things, I wanted a way to store some files there that _only_ I could access. I could switch to a provider that had stronger privacy features but I really love Dropbox's convenience and simplicity. So, I built a solution:
http://safeboxapp.com
The app takes files it finds in ~/Safebox and encrypts them using AES-256 and stores the files in a subfolder of ~/Dropbox. When it sees new encrypted files in that folder, it decrypts them back to ~/Safebox. From then on, changes in either folder are automatically synchronized. The filenames and folder names are encrypted as well.
From a user perspective, you simply use ~/Safebox instead of ~/Dropbox for files requiring extra security.
It's packaged as a Mac OS/X app (and soon as a Windows app). We haven't decided pricing yet.
I'd love to hear your thoughts!!
Thanks, Denis
http://safeboxapp.com
From a pricing perspective, I think your market might be limited in that companies needing security would probably purchase a separate solution and not use Dropbox.
But you might be able to get a revenue stream from prosumers / tech consumers. And your costs wouldn't be high since you ride on top of the dropbox service. And I could be wrong about the market of course. ;-)