We had originally planned to go all-in on passkeys for ONCE/Campfire, and we built the early authentication system entirely around that. It was not a simple setup! Handling passkeys properly is surprisingly complicated on the backend, but we got it done. Unfortunately, the user experience kinda sucked, so we ended up ripping it all out...
That is also the case with passkeys, if you so choose. Though they are functionally similar to your SSH key, they don’t just allow you to utilize the key just by having it loaded onto your device. When you go to use a passkey you need to authenticate your key upon use, and you can do that biometrically. For example let’s say I have a passkey on my phone which is currently unlocked and in use. If somebody runs over and steals the phone from my hand and prevents it from locking, and then attempts to authenticate to a site using my passkey, they won’t be able to.
Right, but I can’t require a second factor on a different device that operates outside of my primary device’s trust store. I’m sure there is some way to make my desktop hit my phone up directly and ask for fingerprint auth before unlocking the local keystore, but that still depends on the security of my device and my trust store. I don’t want the second factor to be totally locked to the device I’m running on. I want the server to say, “oh, cool, here’s this passkey. It looks good, but we also need a TOTP from you before you can log in,” or “loving the passkey, but I also need you to respond to the push notification we just sent to a different device and prove your identity biometrically over there.” I don’t want my second factor to be on the same device as my primary factor. I don’t know why a passkey (potentially protected by local biometric auth) + a separate server-required second factor (TOTP or push notification to a different device or something) isn’t an option.
EDIT: I could make it so a fingerprint would decrypt my SSH key rather than what I have now (i.e. a password). That would effectively be the same number of factors as you’re describing for a passkey, and it would not be good enough for my organization’s security model, nor would it be good enough for me.
I mean you don’t have to authenticate your passkey with biometrics, you can use a password.
I guess I’m not really picking up on what the benefit is you’re going for. You already have a What You Have and a What You Know or What You Are, and you want a second What You Also Have thrown in there. I mean, I guess having that as an option couldn’t hurt. but I also don’t think it’s really necessary.
Passkeys are already more secure than what you’re doing now. If what you’re aiming for is for them to be even more secure than that, then that’s an admirable goal. But as of right now they are worth it just for the fact that they’re more secure than existing solutions.