Is there a way to passphrase protect my koji cert?

[Bruno Wolff III]

While replacing my koji cert yesterday I was interested in adding a
passphrase to slow down exploitation if my home desktop got compromised.
I've look through some of the documentation for maintainers and I haven't
seen any instructions on how to protect it with a passphrase. Is this
possible? (In a way compatible with fedpkg and koji command line.)