Web Key Directory (WKD) allows an OpenPGP client to discover a public key from an email address.
It works by converting an email address e.g. hello@fluidkeys.com into a special URL and requesting it by HTTPS:
https://fluidkeys.com/.well-known/openpgpkey/hu/im4cc8qhazwkfsi65a8us1bc5gzk1o4p
This returns the OpenPGP in binary format (not ascii-armored).
As a temporary solution we're using Github to host our public keys, and using a simple redirect in our nginx configuration:
# /etc/nginx/sites-enabled/fluidkeys.com_HTTPS
rewrite ^/.well-known/openpgpkey/(.*)$ https://github.com/fluidkeys/web-key-directory/raw/master/.well-known/openpgpkey/$1 redirect;
In the future Fluidkeys will host and automatically update our WKD keys.