!!! Overview
[{$pagename}] The [Web Authentication API] ([WebAuthN]) implies a specific [ABSTRACT] functional model for a [WebAuthn Authenticator].For [WebAuthn Authenticator], this model defines the logical operations that they [MUST] support, and the [data] formats that they expose to the [WebAuthn Client] and the [WebAuthn Relying Party]. However, it does not define the details of how [authenticators] communicate with the [Client Device], unless they are necessary for interoperability with [WebAuthn Relying Party]. For instance, this [ABSTRACT] model does not define 

* [protocols] for connecting [WebAuthn Authenticators] to [WebAuthn Clients] over transports such as [USB] or [NFC]. \\ 
* define specific [error codes|Result Codes] or methods of returning them.

[{$pagename}] does define [error] behavior in terms of the needs of the [WebAuthn Client]. Therefore, specific error codes are mentioned as a means of showing which error conditions [MUST] be distinguishable (or not) from each other in order to enable a compliant and secure client implementation.

!! [{$pagename}], [FIDO-CTAP] and [CTAP2]
[FIDO-CTAP] is an [example] of a concrete [Implementation] of this model, but it is one in which there are differences in the [data] it returns and those expected by the [Web Authentication API]'s [algorithms]. 

[CTAP2] response messages are [Concise Binary Object Representation] ([CBOR]) maps constructed using [integer] keys rather than the [string] keys defined in this specification for the same objects. The client is expected to perform any needed transformations on such data. The [FIDO-CTAP] specification details the mapping between [CTAP2] integer keys and [WebAuthN] string keys.

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
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* [#1] - [WebAuthn Authenticator Model|https://www.w3.org/TR/webauthn/#sctn-authenticator-model|target='_blank'] - based on information obtained 2020-10-24