determine existing gpg key identification
From thelinuxwiki
$ gpg --fingerprint jsmith@abccorp.com pub rsa2048/BXZM9213 2014-01-24 [expires: 2019-01-23] Key fingerprint = 9A27 0DC4 34F9 31C5 5676 7F61 BD58 AFA3 AEBF 6248 uid [ultimate] john smith <jsmith@abccorp.com> sub rsa2048/7CE1803D 2014-01-24 [expires: 2019-01-23]
the key id or gpg-id above is BXZM9213