Securely Encrypting Files – Mac OS X

Sharing documents that contain sensitive, personal information, can be risky. Varying levels of identity theft can result if your documents aren’t properly protected.

There are any number of methods to securely share such documents. Here are a few of the simpler methods:

  1. Print the documents, or copy the files onto portable media (CD or flash drive), and send by Postal Mail or hand deliver.
  2. Upload the document files to a secure cloud service (dropbox, etc), email a link to the files, and remove the files from the cloud immediately after they’re downloaded. Note that anyone with access to the link, can download the files as long as they’re available on the cloud service.
  3. Securely encrypt the files and email them. Share the decryption password via telephone.

OS X has compression (zip) software built into the Finder and, with a bit of effort, can be used to encrypt files. Unfortunately, the encryption is relatively weak and it’s hard to do. If your goal is to email files that aren’t sensitive, the built-in compression (no encryption) is the way to go. It makes the files smaller more reliable to email. When sending more than one file, it’s best to copy them to a folder and compress the folder.

To access the Finder’s compression, either control-click the folder and select Compress “folder name”, or select the folder and use the Finder menu File > Compress “folder name”

Continue reading for help with method 3: Securely Encrypting Files.

For Windows, refer to Securely Encrypting Files – Windows

Install Encryption Software

This tutorial utilizes the encryption program Keka:

The App Store version is convenient since it automatically installs and, if your System Preferences allow it, updates. (System Preferences > App Store)

Using the Keka web site download:

  • If the download doesn’t automatically open, find it in your Downloads folder and double-click it.
  • Drag the Keka app to your Applications folder.

Keka Preferences – Compression


Launch Keka and select the menu Keka > Preferences…
An important option is Save to location: The choices are:

  • Ask each time
  • Next to original file
  • Custom folder…

Here you can change where your encrypted file will end up.

Keka Preferences – Extraction


The same saving options are available for extracting (decrypting) files.

Basic Keka Settings

  1. Select 7z (for AES 256 bit encryption).
  2. Method selects the amount of compression.
  3. Enter a password for the upcoming encryption. Twice.
  4. Leave these checked.
  5. Assuming that you’re encrypting only document files (not applications) check Exclude Mac resource forks. If the recipient of your files is a Mac user, it’s optional.

Want to learn more about resource forks? Or even more?

Create the Encrypted Folder (or File)


Drag your folder (or file) onto the Keka window and drop it. The encrypted result will be created at the location you’ve selected.

Note: The Keka window doesn’t appear as above until you drag a folder to it.

To test your encryption, simply drag it onto the Keka window. You’ll be asked for the password and the decryption will commence.

Send the .7z File


Create a new email and drop the .7z file into it. You may want to include some instructions on how to decrypt it. Here’s a sample:

Hello Person,

Here’s the information you requested to process my loan. The file is encrypted using the 7z format.

Please call me at 132-456-7890 to get the password.

If your computer doesn’t have the proper software, it’s available for free:
Keka for Mac OS X.
7 Zip for Windows.

You can find detailed instructions at:
Securely Encrypting Files – Mac OS X
Securely Encrypting Files – Windows

Sending Person

Decrypt the 7z File


Simply drop the 7z file onto the Keka window.