To start using PGP/MIME you first need to link OpenKeychain with K-9. To do this:
Now you’ll need to select a key. Click the ‘My Key’ option.
You’ll be sent a screen in the OpenKeychain app:
Select either a key you’ve already imported/created or create a new key:
See the OpenKeychain website for more information on creating and managing keys.
When composing e-mail with OpenKeychain setup and installed a new pad-lock icon appears in the top left of the composition screen. The icon represents the type of signing and encryption that will be applied to the message.
Signing is the process of authenticating who wrote an email. Encrypting is the process of ensuring nobody but the intended recipient can read it. Signing and encryption both guarantee the email hasn’t been tampered with.
Tapping the icon leads to dialog that allows you to change between one of four states:
When viewing encrypted mail, once configured, K-9 will automatically use OpenKeychain to try to decrypt it with your key and check the signature.
For encrypted and trusted signed messages it will look like this.
Tapping on the green lock icon brings up this modal:
For trusted signed messages it will look like this.
And tapping on the icon brings up this:
Tapping on the ‘View Signer’ option will open the contact in OpenKeychain.