Any reason not to use LUKS on a backup drive?

Question

I have my hard disk encrypted with LUKS, but I make regular backups to an unencrypted external harddrive. Is there any reason I shouldn't setup LUKS on my backup drive as well?

Obviously, the big thing will be keeping track of the key/passphrase, but I believe I have that in hand. I'm more concerned about obsolescence of LUKS, I guess. I want to make sure that if my backup sits around for five or ten years, I'll still be able to mount and access it on whatever linux system I have setup at the time.

Answer 1

It depends on why you need encryption.

If the backup disk is safe at home and you encrypt your laptop because you worry about it being stolen on the go, it's probably fine to have the backup unencrytped. Of course that doesn't help you any if someone breaks into your home.

If you need encryption everywhere, naturally you have to use LUKS for the backups also.

Obsolescence of LUKS? Everything about it is Open Source. It will always be possible to access unless a global nuclear desaster wipes out all copies or something, in which case you probably have other things to worry about.

Answer 2

I'm more concerned about obsolescence of LUKS

What about USB mass storage support? The underlying PATA or SATA disk access? (It's already pretty hard to find motherboards with PATA ports.) How about Linux itself, or USB for that matter?

As frostschutz said, it depends very much on why you are encrypting the main drive.

If your main concern is LUKS obsolescence, there's a pretty simple solution. Make a small unencrypted partition with some basic file system support for which is unlikely to go away (ext2, ext3 or maybe even FAT32) and put ISOs (live and install) for your favorite Linux distribution there, and devote the majority of the disk to an encrypted partition holding the actual backup. Store hashes of the ISOs to be able to detect corruption, and check them on a regular schedule to make sure the drive does not suffer from bit rot. If you need to, just boot from the ISO and mount the encrypted partition. This is trivially accomplished in a virtual machine. Be sure to try it out before you need it; backups are easy, restores are hard.

And major Linux distribution ISOs don't go away easily. Here is year 2000 vintage Red Hat Linux 6.2, which came with a 2.2.14 kernel. I'm sure you can find older if you look around a little.