KI 2085 How to encrypt external storage media - Mac

2023-07-31 (updated 2025-04-30)

Loss of storage medium in connection with moving data between computers has been the source of major data leaks in several cases. If you lose a memory stick, the problem is not only that you lose the data, but the data may be misused if it falls into the wrong hands.

How can you safely move data between different machines? Simple! MacOS has built in tools for you to encrypt sensitive data. This means even if you lose the USB memory stick (or hard drive) the data stored on it is safe and no-one who finds it will be able to access the data without the password.

But this doesn’t happen automatically, so if you’re handling data that is sensitive you need to remember to encrypt the USB stick before you put the data on it. How? Read on…

Insert the device you’d like to encrypt.
Open Disk Tools.
If you don’t see your device, select Show > Show all.
Select the device you want to encrypt by clicking it.
Make sure you have selected the right device, the click on the Delete button in the top-right corner.
Enter a suitable name for the new device.
Click the Setup menu and then select a GUID Map
Click the Format menu and select one of the encrypted formats, either
- For macOS 10.13 and newer:
  - APFS(Case-sensitive, encrypted)
- For macOS 10.12 or older:
  - Mac OS Extended (Case-sensitive, journaled, encrypted)
Choose, enter and vernfy a secure password. Ideally use a password manager such as KeePass or 1Password to generate and store the password. Make it a password that you don’t use for anything else.
Click Delete and then Next.