HOW TO Create an encryption container

1 Use FileVault

By far the easiest way to encrypt a drive is by going into System Preferences > Security & Privacy > FileVault, but you can only use it on your Mac’s boot disk (usually Macintosh HD). You’ll need to log in as an administrator.

2 Choose how to unlock

If you try to restore your FileVault data, you’ll need to unlock it, and you have a choice – you can use your iCloud account, or you can create a Recovery Key. If you go for the second option and lose the key, you’ll be locked out.

3 Change your mind

If you change your mind, removing FileVault is as simple as enabling it was: once again it’s System Preferences > Security & Privacy, but this time you’ll click on Turn Off FileVault. Again, you’ll need to be logged in as an administrator.

4 Encrypt external drives

To encrypt an external drive, use Disk Utility from Applications/Utilities. Select the drive and click Erase; available format options will vary depending on the drive; with modern SSDs you should be able to opt for APFS (Encrypted).

5 Pick a password

Your encrypted data will be protected with a password (unlike with FileVault, you can’t use your iCloud account). That means it’s crucial to pick a password that isn’t easily guessed, and make a note of it somewhere.

6 Encrypt existing data

If the drive isn’t blank, you’ll need to go use Finder. ≈-click on the drive, choose Encrypt and you’ll be asked to create a password; as with a recovery key, if you lose this you won’t be able to restore data from the drive.

7 Encrypt Time Machine

When you pick your Time Machine destination, there’s a tick box for Encrypt Backups. Annoyingly, you can’t just tick it later; to add encryption later, you need to choose a different drive then go back and choose the original drive again.

8 Make an image

To create a disk image in Disk Utility, choose the drive to create it on and click File > New Image. Select a new, blank image of a size you specify so you can add files, or select a folder and create an image from the folder and its contents.

9 Pick your format

There are lots of formats here. A read/write image creates the same .dmg files you might have seen used by app downloads, or you can choose a sparse disk image or sparse bundle if you want your disk image to grow as required.