Hardware Security SDK is not a specific platform or service that supports AUTHENTON#1 FIDO2 CTAP2.1 keys for multi-factor authentication.
Rather, it is a software development kit that provides tools and resources for building secure hardware-based applications and solutions that can incorporate AUTHENTON#1 FIDO2 CTAP2.1 authentication.
Therefore, the steps to register a AUTHENTON#1 FIDO2 CTAP2.1 key with Hardware Security SDK would depend on the specific application or solution being developed using the SDK.
In general, the process would involve integrating AUTHENTON#1 FIDO2 CTAP2.1 support into the application using the SDK's tools and APIs, and then registering the AUTHENTON#1 FIDO2 CTAP2.1 key with the application according to its specific authentication requirements.
The documentation and resources provided by the Hardware Security SDK can provide more detailed guidance on how to integrate and register AUTHENTON#1 FIDO2 CTAP2.1 keys for authentication within a specific hardware-based application or solution.