The implementation ends up being a new key gets generated per domain, which is actually what you should be doing with your ssh-keys as well something like "ssh -i server.domain.net server.domain.net"

Because webauthn is such a nonstarter I am actually going to try and half-ass it using SubtleCrypto.sign() and friends. sort of mimic the webauthn api. This is really just a weekend project, nothing important. but I feel really stupid every time I work on it, mainly because of how ridiculous it is to have your key infrastructure managed by the service you are logging into.

However due to domain sandboxing I have half convinced myself it is as secure as using a cookie to auth the person, perhaps even a little better because I never have to see a secret. then fall into despair again on how stupid this whole endeavor is, because I could see the keys anytime I want to. (sighs, shakes fist at the sky) why could you have not made webauthn usable?

What specific gripes do you have with WebAuthN that makes you want to reimplement it?

All the problems I have with it as a user originate from either reyling parties doing dumb/user-hostile things (enforcing resident keys even though I'm perfectly capable of remembering my email address or my username, improperly layering WebAuthN with existing second factors etc).

These are possible because WebAuthN is trying to provide for many use cases at once, but I've never felt like it was missing something, and user-friendly behavior is definitely possible. I've seen many examples at this point.

No good way to manage(save/restore) the keys. but the real killer for me was that it requires a hardware token to work, while a hardware token is better, it sort of sucks as a hard requirement for all users.

Really, I don't want to reimplement webauthn, I will will probably be sticking with basic auth as it just works. However, I was hoping to finally get decent public key auth. and webauthn is close, really close, but it is like the designers gave up at the last second and said "no, we don't want this to work in the general case", all it would have took was to say software token are an ok fallback. I was so close that out of frustration I spent a weekend with an experiment to make public key auth work for everybody. It works, but is a bit pointless as then I, the service needing to authorize somebody, is the same person providing them their public key management system. I might as well cut out the all the ridiculous bit twiddling and just use cookies for all the security that grants the end user.