GPG keyrings can be used as a source of trust in terms of who should be allowed to SSH into a server.
This repository contains a script that may be used as an sshd
AuthorizedKeysCommand.
You will need to create a user specifically to run gpg-authorized-keys. It's
recommended to use systemd-sysusers to create this user, or alternatively you
could run:
useradd gpg-authorized-keys
In your sshd_config add:
AuthorizedKeysCommand=/path/to/gpg-authorized-keys
AuthorizedKeysCommandUser=gpg-authorized-keys