How to Create an Encrypted Local Drive

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You’ve surely heard about encrypting your drives, your phone, or your internet traffic before. If you’re not a “computer type,” you likely don’t know what we’re talking about. How can you protect your files if you don’t know how to do it? In this short tutorial, I’ll walk you through creating an encrypted disk image on macOS. Think of it like an ultra-secure USB drive that lives on your computer. You can then use this disk image to store important financial documents, password hints, or private photos. It’s likely a better idea to encrypt only your most important information, so here’s how you can do it in just a few easy steps on your Mac!

Note: for this tutorial, I’ll be using macOS Mojave, an as-of-yet unreleased version of macOS. However, the primary difference you’ll see from that will be dark windows. I’ve got my machine locked in dark mode, because I absolutely love it. Your windows will be white, that’ll be the only real difference.

You’ll be able to get this by downloading the macOS beta, or by just waiting about two more weeks.

Creating the Drive

Open Disk Utility. You can find this in Applications > Disk Utility. Or, press Command + Space to open Spotlight, and type in “Disk Utility” and hit enter. That’s my favorite way to do it.

Next, go to File > New Image > Blank Image. You can also hit Command + N, but that doesn’t make for a very good screenshot, does it?

Next, ignore everything else for a moment. Enable encryption on the drive.

Go down to Encryption, tap on the option, and select 256-bit. If you’re reading this in 2024, select 1024-bit, or whatever the highest level of encryption you’re using is.

You’ll be prompted to enter a password now. Make sure it’s a strong one, but memorable. You can have macOS remember the password for you, but that defeats the purpose of having this separate secure drive. I recommend using a service like 1Password to write down a hint for your password, so you don’t forget it.
Next, you’ll want to do a few things.

1. Give the DMG file a name. This is the file you’ll see on your Desktop (or wherever you decide to store the file).
2. Store your file somewhere. I keep mine on the Desktop, but you can put yours anywhere.
3. Give the drive itself a name. This is the name that you’ll see when you mount the disk. This will be the name of the drive that’s mounted on your computer when you open the DMG file. It can have the same name of the DMG file, if you want.
4. Next, decide how large the file should be. I went with a small one, 128 MB, but you’ll need to decide how large you want it. 1GB isn’t a bad size. If you’re storing a lot of images though, you may want to go with 5GB. If it’s mostly text files and documents, 1GB will likely suffice. Don’t worry about size too much. If you run out of space, you can just create a new disk image, and move everything to that.
5. Finally, there’s the tricky one, if you don’t know your own computer very well. The format. It’ll likely say “macOS Extended (Journaled).” That’s okay. No matter what Mac you have, that’ll work. However, if you have a new Mac, with a solid state drive (not a hard drive or fusion drive), you’ll likely want to select APFS, for the Apple file system drive. This will work better for SSDs, but, really, any macOS model can use the macOS Extended Journaled format, so, if you’re not sure, go with that.
6. Hit save, and you’re done. The drive will automatically mount.

Now we have an empty drive. What now?

Using the Drive

You can use your new drive like a USB drive. Only, to insert the drive into your computer, you have to open the DMG file and enter a password. Every time you open the DMG file, you’ll need to enter your password. After that, it’s just like any other drive.

You can save files to it just like any other disk drive. It’ll appear under locations.

Just be sure to eject it when you’re done, that way someone else trying to access it will be locked out thanks to your password. You can do this by right, two finger, or control clicking the drive, and selecting eject. You can also do it by dragging the drive to the trash, or by clicking the Eject symbol next to it in the finder. The next time you want to use it, just double click your DMG file, type in your password, and you’re good to go.

This drive can be very useful. For example, let’s say you’re not encrypting your Mac’s drives or backups. This could prevent someone from getting into your files, even if they can get into everything else. It’s the best way to keep your stuff safe.