I knew I had to do something about the data on my laptop (Ubuntu 8.10), so I sat down one day to figure out what to do. I knew the tools were there, but where to start? Almost absent-mindedly I right clicked on the folder I needed to encrypt, and saw that there's an "Encrypt..." command right there on the menu. (Note that you have to be pointing at the file or folder in the right pane of the Nautilus file manager.)
"That was easy," I said to myself. I selected the "Encrypt..." command. Since this was the first time, it took me through a number of steps to generate some keys. I just followed the dialogues. On my Lenovo x300 it took several minutes to generate the keys after I got through the dialogues. I was starting to worry if something was wrong, but patience prevailed.
Once the key is generated, I could go back to encrypting my folder. I selected the option to "Encrypt all files together in a package." After it was done, which wasn't long at all, I was left with the original folder, the folder.zip file, and a folder.zip.pgp file. The ".pgp" file is the encrypted one, so I deleted the original folder and the folder.zip file.
Then I had to make sure that the files can't be reconstructed by someone with the right tools and access to my laptop. I opened a terminal window and did this:
dd if=/dev/zero of=junkThe first command takes quite a while. It writes zeros to all the free space on my disk. The more free space, the longer it takes. When it fills the disk, it stops. The second command deletes the file, so I have all my free space back. (If you don't know why I did this, read the last paragraph of this article.)
I've heard that there are ways to get data back from disks even if they've been completely re-written. Leave a comment if you know more about the practicality of restoring zeroed hard drives. The above approach certainly foils a relatively determined attempt to get the data back, and should put you in good stead with your privacy people.
Note that this process still isn't one I'd want to do every time I had to access some personal health care data on my laptop. It's a manual process, meaning I might forget to do it or won't have time to do it that one time just before I leave my laptop in the rental car at the airport. It also takes time, especially if you have a lot of free space on your disk.
If you don't know why you have to write zeros on all your free space, here's why: When you delete a file on your computer, you don't actually erase the data. You just mark it as available for re-use. Someone with the right knowledge (and there are many who have this knowledge) can reconstruct old data on your disk. If you write zeros over the free space, you ensure that there's no data for them to reconstruct.