Dangerous Cryptoloop Voodoo

Today, I wondered whether I could use cryptoloop to encrypt an already existing partition, in place. This could be useful if you have a large hard drive that you want to encrypt, but you don't have anywhere to copy the files as an intermediary. To test the theory that it was possible, I backed up my flash drive and tried. Here goes!

Encrypting

We're using losetup to create a virtual block device piped through the encryption algorithm to the original partition. That's pretty easy.

Danger, Will Robinson!

This is the dangerous step. We're block by block copying each original block and immediately sending it back through the cryptoloop device, whch encrypts the data and puts it back on the device itself.

Using The Device

Now that we've in-place encrypted the device, we can try mounting it again.

It works. Of course, I make no guarantees that this will work for you. If you're willing to risk it, good luck. Mind you, doing this while the drive is mounted is an even worse idea.