Yes it is possible. The best way to archive this with a per file encryption is with encfs:
The general principle is that you have a (optionally hidden) encrypted folder inside UbuntuOne/Dropbox where your files are stored, but you access them though another folder, where the decrypted files are shown. Any File you add to the decrypted folder will be encrypted and put into the encrypted folder:
Decrypted folder ←encfs→ Encrypted Folder (inside UbuntuOne/Dropbox)
On another computer the encrypted folder is synced by UbuntuOne/Dropbox and can also be decrypted on the fly.
Installation:
Install encfs version 1.7 or greater
sudo apt-get install encfs
install gnome-encfs-manager:
sudo add-apt-repository ppa:gencfsm/ppa
sudo apt-get update && sudo apt-get install gnome-encfs-manager
Setting up the Drive on the first computer:
- Create a (hidden) directory inside Dropbox/Ubuntu One to use as for the encrypted files
- Start gnome-encfs-manager and set up a new stash (click on the plus sign)
- Set the directory to encrypt to a (hidden) folder inside your Dropbox/Ubuntu one folder
- Set the mount directory wherever you want (default is fine)
- enter a good password (30 random chars...) and click "Create"
- edit the new stash so it is mounted on startup and the password is saved in the gnome keyring
You should now have your encrypted drive mounted (it will be displayed like a mounted usb-drive)
Importing the drive on other computers:
- Wait for all files to sync
- Start gnome-encfs-manager and set up a new stash
- Set the directory to the previously created folder inside your Dropbox/Ubuntu
- encfs-manager will detect the drive and import it
- Set the mount directory wherever you want (default is fine) and click "Import"
- edit the new stash as desdribed above
- you will be asked for your password on first mount
Cross Platform compatibility:
- This is cross compatible with Android when using Encdroid (open source, recommended) or Cryptonite (open source). Both Android Apps support Dropbox and should also work with UbuntuOne using local folder decryption (in combination with an UbuntuOne client which syncs your files onto the SD Card)
- This is probably also compatible with windows using encfs4win or other software.
Ubuntu One uses Amazon's S3 service in datacenters around the world. There are no UK datacenters listed on S3's website, though this could change.
To answer your question directly, S3 Datacenters (holding your Ubuntu One data) are in the following countries: USA, Ireland, Singapore, Japan, and Brazil. None of those countries are part of the UK.
If you don't trust one or more of these governments with your data, see this question on encrypting your data in Ubuntu One.
EDIT: Here is the Ubuntu One technical details page confirming they use S3
Best Answer
According to the US, if a company is registered in the US, all data they hold anywhere in the world is fair game. So this includes all servers used by Microsoft, Amazon and Google anywhere in the world according to the US. And in the last few days there has been another example of this:
"Google is the next major company to admit Patriot Act issues, as it admits to handing over data held in a European datacenter back to U.S. intelligence." ZDNET, August 11, 2011
I am not a lawyer and not related to Ubuntu One/Canonical and not a lot of users here are legal experts with knowledge about this situation so an answer to your question will all be conjecture. And it also depends on how stubborn the EU is about enforcing own law and opposing the US Patriot Act.
Ubuntu One Terms of Services
Ubuntu One is based in the UK so the company is subject to the EU laws and the
European Data Protection Directive. So the answer to your question should beno Ubuntu one is not affected by this if you store the data on a EU serverIf you want to make sure before you start using Ubuntu One that your data will not be handed over to the US you can contact them yourself and get an official responce (from Ubuntu privacy policy):
Any data stored on a cloud worth protecting should be encrypted. Might not stop the US from getting it and also might not stop the US from decrypting it but it should be made as problematic as possible ;-)