XEP-0189 is a bit heavy on the XML. Perhaps it would be good to also specify how to include the (armored?) ASCII output of a GPG public key or X.509 certificate, such as:
http://www.saint-andre.com/me/stpeter.asc http://www.saint-andre.com/me/stpeter.pem Peter -- Peter Saint-Andre https://stpeter.im/
smime.p7s
Description: S/MIME Cryptographic Signature
