Passkey is some sort of specific unique key to a device allowing to use a pin on a device instead of the password. But which won’t work on another device.
Now I don’t know if that key can be stolen or not, or if it’s really more secure or not, as people have really unsecure pins.
I’m not sure if this is universal or specific to the last site I tried to use my Yubikey with as a passkey, but it only would allow it to be used as 2FA, not actual passwordless authentication.
I assume this is because Yubikeys don’t create a secret for each individual website I suppose? Not exactly sure about that one.
The site likely didn’t support passkeys. But passkeys are basically webauthn passwordless login, and per the yubikey docs they support that.
See https://www.yubico.com/authentication-standards/fido2/ and https://fidoalliance.org/passkeys/#faq for more info. See also https://support.apple.com/guide/iphone/use-passkeys-to-sign-in-to-apps-and-websites-iphf538ea8d0/ios specifically the bit about adding a passkey to a physical key.
Google definitely supports passkeys, and they were one of the sites that did this. I’ve just replied to another comment regarding this. I wonder if the Yubikey 4 (I’m not sure how to tell which one I have, since they look about the same) just doesn’t support passkeys, which would be… unfortunate.
It’ll be even more unfortunate if there’s a weird mix of sites that support the Yubikey as a passkey and some only support it as a passkey. My Pixel is supported as a passkey, but Firefox on Linux doesn’t support this - only on Windows and macOS. I believe Chrome/Chromium does, which is equally as frustrating as my Yubikey possibly not supporting passkeys.
Per Yubico’s specs on the Yubikey 4, it does not support FIDO 2 resident credentials, meaning it does not support Passkeys.
Compare to the specs of the Yubikey 5C NFC or Yubico Security Key C NFC, which both have this section:
See also Yubico blog post with an FAQ about passkeys:
I wouldn’t run out right now and buy a Yubikey to store Passkeys given the 25 key limit and the likelihood that Yubico releases a new key that supports storing far more of them, but if you do, the $25 Security Key series is the cheapest option.
The credential needs to be set as discoverable and some other stuff to work for passwordless login (the token must store site specific data)
You would need to reregister it as passwordless to not just use it as 2FA after having entered a password (meanwhile standard 2FA with webauthn don’t store anything on the token, the website sends encrypted credentials to the token which only the token can decrypt and then authenticate with)
Both the website and your physical security token must support the right type of webauthn credentials (the token has storage for a certain number of slots with “discoverable credentials”).
Passkeys is a variant of the same which is bound to your device’s own TPM / SE security chip or equivalent, plus a synchronization feature for backups.
You can use Yubico keys as your passwordless logins. Both Google and Microsoft have this option.
Strangely enough, Google lets me “add” my Yubikey as a passkey, but then does not let me sign in with it due to it not being “recognized”. If I remove it as a passkey, and only use it as a 2FA token, attempt to sign in and use the “Enter your password” option, it will then let me use the key after I’ve entered my password as a second factor.
So it seems Google has removed the error (or its not triggering anymore) as they will have been one of the first sites I tried to create a passkey for, but it still does not let you use it as a passkey.
I haven’t encountered this issue, yet. I’m using LibreWolf browser (v118.0) and tested logging in my Google and MS account passwordless. BTW, I have Yubico Security Key NFC (the blue one).