Re: [webauthn] Why does WebAuthn require a challenge when asking the client to register a new credential? (#1355)

@marekciupak Correct, if the attestation statement format is `"none"` then the registration response is not signed. Similarly, if the attestation statement format is `"self"` then the registration response is signed by the credential private key - but the corresponding credential public key is conveyed in the same message, so an attacker could easily replace both the public key and the signature (or just replace it with a `"none"` attestation), so the self attestation signature only protects against accidental data corruption but not against intentional manipulation. The challenge does have some value for the other attestation statement formats, though. But in general, WebAuthn credential keys are "trust on first use" - see also [ยง13.4.4. Attestation Limitations](https://www.w3.org/TR/webauthn-2/#sctn-attestation-limitations).

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Received on Saturday, 28 August 2021 13:49:23 UTC