Encrypt Dropbox Folders on Ubuntu With CryFS

(updated )

Source

Introduction

This is one way to encrypt the contents for cloud-synchronized folders using CryFS. I'm going to illustrate it using the Dropbox folder that the dropbox client creates.

Encrypt the Folders

Install It

Ubuntu currently (November 10, 2018) has CryFS as part of its packages so you can install it with apt.

sudo apt install cryfs

Create the Target and Source Folders

The cryfs command will create the two folders and set them up for you. The syntax is cryfs <target> <source>. The target will contain the encrypted folders so it will go in the Dropbox folder, while the source will hold the unencrypted files.

cryfs Dropbox/encrypted dropbox_source

This is the same command you would use on another computer to set-up the existing encrypted folder on your new computer. The source folder can be named differently, but the target folder and the password need to be the same one you used when you created it. The files in the source go away when you unmount it (see below) so you will have to re-mount it whenever you unmount it or log out or restart your computer.

Note: The cryfs tutorial has a warning that if two different computers access the mounted folder at the same time it can corrupt the files so you have to make sure to unmount it on one computer before mounting it on another. This seems like a really bad thing, but I guess you should/oughta make backups of the unencrypted stuff just in case.

Unmount It

The old way to unmount it was using fusermount but they've added a cryfs-unmount command which you can/should use instead.

cryfs-unmount dropbox_source

This was the old way.

fusermount -u dropbox_source

Since you are doing all this within your home directory you don't need root privileges (except to install cryfs with apt).

References

  • I got this from Linux Babe.
  • But the CryFS Tutorial is pretty straight-forward, it just skips the part about installing cryfs.