What does HackerNews think of SoftU2F?

1. Windows: https://github.com/frankmorgner/vsmartcard/tree/master/virtu..., which is a fix-up of the older https://www.codeproject.com/Articles/134010/An-UMDF-Driver-f..., and https://github.com/Watfaq/SoftU2F-Win/tree/master/SoftU2FDri.... Note that neither of these actually implement CTAP2.

2. Linux: There's plenty to refer to on HID gadgets, but https://blog.hansenpartnership.com/webauthn-in-linux-with-a-... and the code at https://git.kernel.org/pub/scm/linux/kernel/git/jejb/fido2-c... were my entrypoint and cover the whole idea of WebAuthn in software.

3. Mac: I ended up not implementing a Mac version, but GitHub themselves used to support a CTAP1/U2F software authenticator, now archived at https://github.com/github/SoftU2F. I was going to work from that.

For the service I looked at different software "devices" interfacing with these kinds of drivers (or just the browser directly in Firefox's case).

1. Generic NIST SP 800-73 PIV: https://github.com/CCob/PIVert. Very limited scope, pentest tool with no extraneous features. It uses the BixVReader driver.

2. U2F: Just the corresponding driver repos I think.

3. CTAP2: Firefox Soft Token code, https://github.com/ellerh/softfido, https://github.com/bulwarkid/virtual-fido (the one you found).

We've used https://rsc.io/2fa to share TOTP keys between multiple individuals. We store the secret key in a shared password store that's also behind a separate 2FA login.

For U2F, check out https://github.com/github/SoftU2F

I believe Chrome’s dev channel also has experimental soft webauthn support.