1. Go to Settings -> Messages -> Encryption.

2. Click on your Personal key that you would like to revoke.

3. Click on Revoke.

4. Enter your OpenPGP key pair passphrase and click on Ok.

• Read the warning message carefully before proceeding.

• If you already have published your Public key onto Public key servers, then check the box Publish on public key server so everyone can see that it has been revoked and you no longer use it.

5. Click on Revoke.

After you’re done revoking your OpenPGP key pair, send an email to all of your contacts and let them know that you don’t use that key anymore and (if possible) provide them your new public key as well.
While you can still decrypt emails using an expired and/or revoked OpenPGP key pair, you cannot sign emails using your expired and/or revoked OpenPGP key pair.
Also sending an encrypted email using an expired and/or revoked public key is not allowed.