Amiibo

Amiibo are NFC figures made by Nintendo, used in games in different forms (different in each game). It can be used with the New3DS and the Old3DS with an IR peripheral.

Technical specifications

See also here.

Specifications can be found on this image, which is a compilation of screenshots made by scanning a Samus amiibo with the Android App "NFC TagInfo":

Most of the NFC pages are encrypted. This includes the actual Mii data for the owner, an UTF-16 string for the Amiibo nickname, etc.

The NFC tag for Amiibo is NTAG215.

The NFC 32bit password for the PWD_AUTH command(for enabling write-access to the encrypted NFC pages / etc), appears to be generated from unknown data that doesn't change when the Amiibo data pages are being updated.

Each page is 4-bytes, the following is the structure of the NFC page:

NFC page	Total pages	Raw byte offset in EEPROM	Total byte size	Description
0	4	0x10	0x10	Same as standard NTAG215: 9-byte serial-number, "internal" u8 value, two lock bytes then the "Capability Container (CC)" page.
4	8	0x10	0x20	SHA256-HMAC over 0x1DF-bytes: first 3-bytes are from the last 3-bytes of page[12], the rest is over the first 0x1DC-bytes of the plaintext data following this hash(see page[13]).
12	1	0x30	0x4	Unknown. Last 3-bytes here are used with the above HMAC.
13		0x34		The system crypts 0x1A0-bytes starting here.

Structure of plaintext data from page13

Offset	Size	Description
0x0	0xB0	Amiibo settings are stored within here.
0xB0	0xD8	AppData, for the user-application with the programID specified in the above Amiibo settings. The data stored here is application-specific.
0x188	0x18	Not used in "decrypted" form, since this isn't encrypted to begin with.

Structure of Amiibo settings

Offset	Size	Description
0x0	0x1	Unknown. The low 4-bits here are copied to the struct used with NFC:GetAmiiboSettings.
0x1	0x1	Unknown. The low 4-bits here are copied to the struct used with NFC:GetAmiiboSettings.
0x2	0x2	?
0x4	0x2	u16 big-endian, unknown.
0x6	0x6	?
0xC	0x14(10*2)	UTF-16BE Amiibo nickname.
0x20	0x60	Owner Mii.
0x80	0x8	Application programID for the AppData, zero otherwise.
0x88	0x4	?
0x8C	0x4	?
0x90	0x20	Probably a SHA256-HMAC hash.