[tor-relays] Storing ed25519_master_id_secret_key[_encrypted] on a smartcard?

Dear fellow relay operators,

currently, I'm operating a Tor relay (Middle/Guard) and a Tor Bridge.

Offline keys [1],[2] are a good way to secure a Tor relay, but I'm wondering if there is a standard way or something like a hacking guide how to store your ed25519_master_id_secret_key[_encrypted] on a smartcard or hardware token like a Nitrokey or Yubikey? This would even be more secure than storing it on a "normal" USB device.

Unfortunately I have not found much about this on the internet.

Kind regards telekobold

[1] https://support.torproject.org/relay-operators/offline-ed25519/ [2] https://gitlab.torproject.org/legacy/trac/-/wikis/doc/TorRelaySecurity/Offli...