![]() ![]() For example, the authenticator may ask the user to tap on the authenticator to confirm user presence. Otherwise, it performs a simple user presence test. This WebAuthn call is used to tell the web browser to ask an attached authenticator (embedded or via USB, NFC, etc.) to generate a new credential (private/public key pair) using the authenticatorMakeCredential() operation, store it locally (or encrypt it so that only this authenticator can decrypt it and return it so that it can be sent to the RP for server-side storage there).īefore generating a new credential, the authenticator verifies some of the received parameters and performs user verification if the authenticator supports it (for example, ask for a biometric or PIN). The client-side code typically executes when the user clicks a “Register” button on the page. The relying party’s web app serves a registration page which contains client-side Javascript code that calls () with some parameters generated by the RP, such as a challenge, randomly generated server-side, to prevent replay attacks, and a list of public key algorithms that the RP supports. The web browser’s WebAuthn implementation will make calls to authenticators using the CTAP2 protocol, which uses a binary format named CBOR to encode data. Registration flow Figure: Registration flow, from the official WebAuthn specificationĭuring registration, the user who registers a new account on a relying party (RP), with their authenticator, will use their web browser, which implements the WebAuthn specification. Let us see how these operations work and discuss their security. WebAuthn defines two operations: registration and authentication. ![]() ![]() In this blog post we will describe FIDO2’s security model and discuss advanced topics at the core of the protocol such as attestations. It is recommended to first read the introduction about what FIDO2 is. This article is an advanced blog post about FIDO2. The attestation section below was updated to explain a possible attack scenario. Update : As pointed out by a reader (thank you!), attestations do not protect against man-in-the-middle attacks where an attacker owns a genuine authenticator of the same model as the victim’s. ![]()
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