Amiibo Encryption Key _top_ Online

Nintendo attempted to mitigate the breach by introducing new "fixed" key sets in subsequent firmware updates. Theoretically, this would have rendered the old keys obsolete. However, backward compatibility with the existing installed base of Amiibo figures (which were signed with the old, "unfixed" keys) meant that the consoles could not strictly disable support for the original keys.

When you tap an amiibo to a Switch, the console reads the user data and the appended "HMAC tag." The console runs the user data through the AES-128 algorithm using the internal secret key. It generates a new HMAC. If the generated HMAC matches the stored HMAC on the chip, the data is authenticated. amiibo encryption key