Mac OS X: Protect file with password - how it works

This practical tip describes how to protect a file with a password on Mac OS X. If you want to hide sensitive files from other users, you can find out in the following article which steps you need to take into account.

Mac OS X: Protect files with an encrypted image with a password

You don't need an external tool to lock files on your Mac with a password. You cannot protect individual files, you can create an image with a secured folder in which you insert the files. That's how it's done:

1. First open the "hard disk diagnostics program" by tapping the magnifying glass next to the time in the menu bar and entering "hard disk diagnostics program". Click on one of the results next to "Programs" or "Top hits".
2. Select the button with the signature "New Image" in the hard disk diagnostics program.
3. Select an appropriate size for "Size" for the encrypted folder, the "128-bit AES encryption" under Encryption and for the "Image format" lastly "Growing image".
4. Before you click "Create", name the image and specify the location.
5. Now set a password that is as memorable and secure as possible. If necessary, deactivate the "Save password in keychain" option by removing the check mark.
6. The next time you open Finder, you will see the image you just created in the location you specified in step 4. Double click on it.
7. The folder now appears on the left in the Finder under "Devices". Tap on it.
8. Paste the files you want to encrypt into the folder.
9. Eject the image by right-clicking on it in the Finder and choosing "Eject Image".
10. If you want to access the folder again, you have to mount the image again by repeating steps 6 and 7.
11. The folder is now encrypted. Repeat step 9 as soon as you want to lock the file again.

The steps refer to Mac OS X 10.9.4. If you are using a different Mac version, the instructions may differ. You can read more about this in the articles "Mac: Show hidden files and folders" and "Mac: Lock screen".