I think a more sensible approach should be similar to `authorized_keys` with `ssh`, where the server keeps a list of public keys for each user, and challenges t

I think a more sensible approach should be similar to `authorized_keys` with `ssh`, where the server keeps a list of public keys for each user, and challenges the user to prove he/she has the corresponding private key for authentication. TLS certificates are notoriously complicated. It may be necessary for server certificates, because the "trust the key on the first connection" is probably insecure when money is at stake, but I don't see any advantages of client certificates over the ssh scheme. If only it were standardized and widely supported.