To interact with Amiibo data on non-Nintendo devices (like an Android phone or a PC), software needs the exact mathematical keys Nintendo uses. In the homebrew community, these are typically found in a single known as key_retail.bin .
and sign the data if the game needs to save new information back to the figure. The Role of key_retail.bin amiibo encryption key
The user known as (a prominent figure in the Wii U hacking scene) managed to extract the key from a retail Wii U game binary. They didn't break AES-128 (which is unbreakable via brute force). They simply read it out of the software that had to use it. To interact with Amiibo data on non-Nintendo devices
: This part contains the publicly readable information, such as the character's unique ID. The Role of key_retail
If you are searching for the hex string yourself, be aware that many security forums have auto-moderators that delete posts containing the raw key. Look for the phrase UnFixedInfo or references to HMAC generation . The key is the grain of sand around which the pearl of the amiibo homebrew community formed. Handle it with care.
When a legitimate amiibo is created at the factory, Nintendo writes the data, then sets irreversible "lock bits" on the chip. You can change the save data (like a game save), but you cannot change the figure's identity (e.g., change a Mario into a Link).