IssueTracker

As of OpenSSH 8.2 (https://www.openssh.com/releasenotes.html) support for keys based on FIDO authenticators was added. The four new formats (2 new key types with corresponding certificate types) are described in https://cvsweb.openbsd.org/src/usr.bin/ssh/PROTOCOL.u2f?rev=HEAD 

They are also listed here:
- sk-ecdsa-sha2-nistp256@openssh.com
- sk-ecdsa-sha2-nistp256-cert-v01@openssh.com
- sk-ssh-ed25519@openssh.com
- sk-ssh-ed25519-cert-v01@openssh.com

When registering these key types an additional piece of information, the "application" (a string typically starting with 'ssh:') is required as it is used to identify the key handle required for signing requests on the authenticator. Thus one cannot simply paste an sk-ssh-ed25519@openssh.com (from ssh-add -L for example) where a normal ssh-ed25519 key is expected.

As of writing, Google Cloud Source Repositories only supports ssh authentication with normal RSA (>=2048 bits), ECDSA and ED25519 keys. We would like to request support for the sk- variants of the elliptic curve algorithms, as we are already using them for authentication in other places and would like to use them in Google Cloud as well.

Thank you