My suspicion: There is a significant chance I will lose access to one or more account by doing this, so I'm not going to until the air clears. I don't trust the motivations of the services pushing it.
This means you never send your private key to the site, so if their database is compromised they only get a public key, which can’t do anything (it is public, after all)
No amount of phishing can get you or your client to hand over your private key, because there is no use case where that is required. There is no possibility of MITM, since your private key is never sent anywhere in any situation.
As for getting locked out of your account, losing your passkey would be the same as losing a password. You would need to follow the site’s password reset flow, and if you can recover from a lost password, you can recover from a lost passkey.
I will poke at this a bit:
> As for getting locked out of your account, losing your passkey would be the same as losing a password. You would need to follow the site’s password reset flow, and if you can recover from a lost password, you can recover from a lost passkey.
Do you think this is one of those scenarios that sounds reasonable at first, but can get torn apart by unknowns, edge cases etc? To use an analogy from a recent HN thread that is stretched a bit, is this like saying "If you use a crypto hardware wallet, you're safe", then reading about compromised hardware wallets due to something outside the assumption set.
A lot of the same Password Manager requirements and best practices apply to Passkey Management such as using strong master passwords or biometric unlocks or device PINs. Using Password Managers that support device bound hardware security enclaves, etc.
But even more so than average Password Management, because Passkeys are public key infrastructure the benefits you get out of the box exceed those of ordinary passwords. One of the factors in most Passkey implementations here is that sites (defined by hostname) all get different public keys. (Users are suggested to use different passwords for every site, but are not required to. Passkeys do that technically and are generally enforced in that effort by browsers and Operating Systems.) Leaking those public keys is no longer an issue (they truly are public keys), and leaked public keys aren't generally useful to other sites and apps. (Passwords that leak and even sometimes salted and hashed passwords that leak are liabilities and can be useful for rainbow table attacks or social engineering attacks or password reuse attacks.)
There are certainly edge cases to Passkey Management but in general the threat models follow Password Management threats: does someone have physical access to your device? Do they have access to your biometrics or device PINs?
But also the blast radius is reduced compared to usual Password Management threats: a single leaked private key generally only impacts a single website/app. Being able to sign a Passkey challenge once doesn't mean unlimited access (a password can be used forever after finding it), because challenges have timestamps and random entropy and generally don't support replay at all.
This is roughly analogous to the difference between swiped/card not present and chip/NFC credit card payments. While a hacked chip/NFC credit card terminal could display a different amount than actually charged, it can't subsequently make additional charges after the card or device is withdrawn.
I generally add keys from two very different Password Managers to every site/app I use Passkeys with. Both Password Managers also sync between multiple devices I own.
Redundancy is already an option. Choice in Password Managers to use for your Passkeys is an option.
I understand that accidental denial of service fear, but the tools exist technically to deal with that fear if you wanted to try to deal with it.
Also, sites can and often do support multiple passkeys, which opens up the possibility of allowing for reliable account recovery using one or more backup devices (one or more YubiKeys, for instance) that is still siginificantly more secure than reset flows using SMS or email.
In other words, my email can be signed in from anywhere on purpose. It's a feature. The chances of me forgetting my password is zero, because I can back it up 7 way to Sunday.
A passkey seems to miss these basic accessibility issues. For a random website, that's fine, but for the service all of websites use to auth me, access is more important than locking it down to one device.
For better and worse, Webauthn is one of the "choose your own adventure" PKI systems where the keys themselves suggest which PKI algorithm/details they use. This is partly because Webauthn has been around a long time and has had to backwards compatibly support a wide variety of physical security keys over the ages.
Most good open source libraries for implementing passkeys will do a good job of limiting passkeys to known good algorithm choices, including any PQ requirements/suggestions. The Passkey standard itself also sets a "higher water" baseline above Webauthn's supported algorithm list.
Also, the same risk applies, but to an even greater degree, with a password.
Little harsh to say I have NO idea what I am talking about, though.
I still don't agree that companies won't revoke their passkeys if we are in a PQ world.
If they don't, you are still in a better place than passwords. Each public/private key pair is unique for every domain, so a compromise in one place is not a compromise in others. Many people re-use passwords (even if you don't).
I liked the idea that passkeys work the same way but now for logging into services like amazon or google etc.
Imagine my face when I learned that that so many interpretations of passkeys exist that actually create that private part in a passwordmanager or chuck it into iCloud or equivalents.
I wondered if the inventor of the private/public keyexchange still lives or if he would spin in his grave hearing what happened...
I would have been on board if the passkeys only existed on your hardware period. I would have accepted that I would need to set up access from devices of my choosing and therefore cannot log into these services from any old "cyber cafe" on a whim.
But I would, as an emergency BCM measure, expect a sort of breakglass phrase that I could obtain and keep safe like at a bank deposit box or similar in case all hardware with keys to said service would die at the same time.
I understand though, that for most all this would look like way to inconvenient and using the cloud instead is so much more convenient which is why they decided to hollow out the concept of the passkey.
I've never fallen for a phishing attack and any attack targeted and sophisticated enough to catch me is probably going to be sophisticated enough to steal/hijack a passkey anyway. In the extremely improbable event that I did get phished and somebody got into my account somewhere, they'd only have access to that one account because unlike most people I don't re-use passwords and recovery would no more complicated than contacting customer service and resetting my password with them.
Considering the horror stories of people who been screwed by using passkeys, I'm sticking with "not worth the trouble"
I have no doubt users will get confused about which password manager they have their passkey stored in, but these are the same users who don't know what a password manager is so they share a password across everything and get hacked regularly.
The benefit of adding additional authentication methods without disabling others is limited, of course, but it can still be useful where, e.g., you're comfortable logging in using a password manager on your own devices but want to use an iPhone or YubiKey to log in from public computers.