Re: [webauthn] Support for FIDO passkey with HMAC-Secret extension (#1830)

> how about using PBKDF2 with the PRF output as salt in conjunction with the user’s password?

I can't give a generic recommendation (nor should the spec, I think) since it'll depend greatly on the application (and since I'm personally not an expert on concerns like this; using a KDF is a pattern I've observed, but I don't know all the nuances around it). But PBKDF2 seems probably fine to me.

> Is the proposed WebAuthn L3 PRF-extension<https://w3c.github.io/webauthn/#prf-extension> function intended to be called from a native app at the device?

Native app APIs are strictly speaking not governed by the WebAuthn spec, so I'll have to pass that question on to platform vendors such as @akshayku, @christiaanbrand, @alanwaketan.

But yes, in a browser that supports the PRF extension you certainly could invoke the extension without involving a remote server. Likewise a client application with access to CTAP2 could implement the same abstractions on top of HMAC-Secret to generate the same outputs as a web version of the app would get from the PRF extension, also without need for a remote server.

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Received on Wednesday, 7 December 2022 09:57:01 UTC