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":

See here regarding the Amiibo encryption.

The NFC tag for Amiibo is NTAG215.

AUTH_PWD

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.

NTAG215 commands

Amiibo reading

• GET_VERSION
• READ, startpage=0x03
• PWD_AUTH
• FAST_READ: startpage=0x00, endpage=0x3B
• FAST_READ: startpage=0x3C, endpage=0x77
• FAST_READ: startpage=0x78, endpage=0x86

Therefore, *all* pages from the Amiibo NFC tag are read, including the configuration pages at the end.

Amiibo writing

• Use the same commands under the above reading section, then use those first 3 commands again.
• Multiple WRITE commands for writing to pages 0x04..0x0C. The first byte for page[4] is zero here.
• Multiple WRITE commands for writing to pages 0x20..0x81.
• Use the last 3 commands from the above reading section.
• WRITE: page=0x04, same data as before except first byte is 0xA5 this time.
• FAST_READ: startpage=0x04, endpage=0x04

NFC pages

Each page is 4-bytes, there is a total of 0x87/135 pages. The following is the structure of the NFC pages:

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	1	0x10	0x4	Last 3-bytes here are used with the following HMAC. The first byte is normally 0xA5. The remaining bytes are initially(before the Amiibo is written to) all-zero. Byte[2] here is increased each time the Amiibo is written to.
?	8	?	0x20	SHA256-HMAC over 0x1DF-bytes: first 3-bytes are from the last 3-bytes of page[4], the rest is over the first 0x1DC-bytes of the plaintext data following this hash.
?		?		The system crypts 0x1A0-bytes starting here.

Structure of the plaintext data

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.