This is a neat trick that people have been doing with Yubikeys for a long time, but from an operational security perspective, if you have a fleet rather than just a couple of hosts, the win is only marginal vs. short-lived keys, certificates, and a phishing-proof IdP.

The integration of the ed25519-sk keys is just so easy and similar to normal ssh keys, so the upgrade is way easier.

You just need to tighten your sshd config, you can even add a "touch required" of the Yubikey to the sshd config. Has been in debian stable since like 11 I think?

So it's super friendly to integrate and very secure, as you need to physically be on your pc, have your yubikey and have your exact pc. So that's a lot of factors.

Lots of ways to establish a persistent presence with a short time life key, especially if it is in env or a file it is trivial to find.

In theory the Linux kernel keyring would help here, even with a tsm or in conjunction with it.

Unfortunately as the industry abandoned the core Unix permission system (uid/gid) all of these methods just get a devfs[null] bind mount.

Only process that also support the traditional co-hosting model like nginx and Postgres do.

We would need nonce keys to gain no value from kernel memory or hardware storage.