Re: [webauthn] devciePubKey extension MUST be supported if passkey is supported (#1691)

I do not believe a separate AAGUID is necessary for Passkey-like solutions (where the private-key and credential are portable across devices); there is an easier solution available within the protocol.

I recommend that one of the bits in [_authenticatorData_](https://www.w3.org/TR/webauthn-2/#authenticator-data) - say, Bit 3 - be used to indicate that the credential with its private-key is portable across devices/authenticators. If Bit 3 is set, the credential and its private-key **are** portable across devices; if it is NOT set, the credential and its private-key are bound to the device on which the key-pair was generated. 

Regardless of AAGUID, an RP will be able to determine, at registration time, whether the credential and its private-key are device-bound or portable. This is easier and faster than having to process an extension (which will also carry additional baggage in the registration response from the authenticator).

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Received on Thursday, 20 January 2022 14:24:18 UTC