[magmastonealex]

There is a revocation system in place (the RevokedKeys directive in the sshd configuration file, which seems to be system-wide rather than configured at the user-level. At least, that’s the only way I’ve used it)

I agree with the sentiment though, it is far less extensive than traditional X.509 certificate infrastructure.

[upon_drumhead]

when I said revocation system, I intended to convey something similar to Online Certificate Status Protocol, rather then a hardcoded list that needs to be synchronized between all the physical servers.

You are correct though, you can keep a list and deploy it to all the nodes for revocation purposes.

It's unfortunate that there's no RevokedKeysCommand to support building something like OCSP.