Encrypt your email on Android with the help of K-9 Mail and APG

If you've been looking for the easiest way to encrypt your mobile email, Jack Wallen has the solution with K-9 Mail and AGP.


There are times when you simply need a piece of outgoing mail to be safe from prying eyes... even when you're on the go. When that becomes a necessity, you need encryption. But how do go about encrypting email when you're on an Android device? Surprisingly enough, it's quite simple--as long as you have the right tools.

Which tools you ask?

K-9 Mail is one of the more flexible and powerful email clients available for Android, and APG is an Android port of OpenPGP. With APG, you can generate and manage keys that are used with K-9 for encryption. APG makes generating and managing encryption keys very simple.

With that said, let's get to the encryption!


This is important. You need to install both applications, but install APG before you install K-9. When you install K-9, it will detect if you have APG installed and automatically enable encryption.

To install APG, follow these steps:

  1. Open the Google Play Store on your Android device
  2. Search for APG
  3. Locate and tap the entry by Thialfihar Communication
  4. Tap Install
  5. Read the permissions listing
  6. If the permissions listing is acceptable, tap Accept
  7. Allow the installation to complete

Once APG is installed, follow the same steps to install K-9 Mail.

Managing keys

The first thing you'll want to do is either generate a new key or import your current key. To generate a key, follow these steps:

  1. Open APG
  2. From the main window, tap the menu button (three dots in the top right)
  3. Tap Create key
  4. When prompted, fill in the necessary information (Figure A)
  5. Once you've filled in the information, tap SAVE

Figure A

Figure A
Creating a key on a Verizon-branded Motorola Droid Turbo.

You'll also need to import the public keys of those you want to send encrypted mail to. There are a few ways to do this:

  • From Keyserver
  • From file
  • From QR Code
  • From Clipboard
  • From NFC

To import a key, do the following:

  1. From the main window, tap the overflow menu on the top left (three horizontal lines)
  2. Tap Import Keys
  3. From the key drop-down, select from where you want to import the key (Figure B)
  4. Follow the steps for importing (steps will vary, depending on the method chosen)

Figure B

Figure B
Importing a public key.

Encrypting mail

It's now time to encrypt email. When you first fire up K-9, you'll need to walk through the account setup wizard. This wizard is as simple as any other, and it'll have you up and running in just a few quick steps (Figure C).

Figure C

Figure C
Setting up an account in K-9 Mail.

Once the account is set up, you're ready to begin encrypting email. Before you encrypt that first mail, let's make the task a bit easier by enabling two encryption settings. Do this:

  1. Open K-9
  2. Tap the menu button, and then tap Settings
  3. Tap Account Settings
  4. Scroll to the bottom and tap Cryptography
  5. Enable both Auto-sign and Auto-encrypt (Figure D)

Figure D

Figure D
Enable both Auto-sign and Auto-encrypt.

When you enable these features, outgoing email will automatically be set to sign and encrypt. The encryption will auto-detect if the recipient has a public key within APG. If not, the mail will not be encrypted.

Here's how to send an encrypted mail:

  1. Open K-9 Mail
  2. From the main window, tap the plus sign [+] to compose a new mail
  3. In the To field, add the address of a recipient whose public key has been imported into APG
  4. If you do not have auto-sign setup, in the composition window, tap to enable Sign
  5. When prompted, select your public key for the signing
  6. If you do not have auto-encrypt setup, tap to enable Encrypt
  7. Compose your email
  8. Tap Send when complete

That's it! Your email has been encrypted.


If you receive an encrypted message, it must have been encrypted with your public key. When you open that mail (in K-9 Mail), there will be a Decrypt button (Figure E). Tap the Decrypt button, enter the password associated with your public key, and the email will be decrypted.

Figure E

Figure E
Decrypting an email within K-9 Mail.

That's it! You've officially encrypted and decrypted email from your Android device. Rest assured that sensitive data you need to send via email is much more safe from prying eyes.

Do you use encryption with email, or do you find it secure enough to transmit sensitive company data? Share your thoughts in the discussion thread below.

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By Jack Wallen

Jack Wallen is an award-winning writer for TechRepublic, The New Stack, and Linux New Media. He's covered a variety of topics for over twenty years and is an avid promoter of open source. For more news about Jack Wallen, visit his website jackwallen....