I recently found myself having the need to revoke an old certificate. The steps are actually quite straightforward, but you do need to have your old revocation certificate to hand.
For more info, visit the GNU Privacy Guard site: http://www.gnupg.org/gph/en/manual.html
Simple follow these steps. In a terminal, issue:
- gpg –import firstname.lastname@example.org (0x712AC328) rev.asc
- gpg –keyserver certserver.pgp.com –send-key 712AC328