Lifecycle management

Card startup

After receiving the ATR from the card, one must select the applet to use it. The applet AID is 0xA0000010000112. This command provides some basic info about the card applet and status flags. The card can be accessed over the contact interface (ISO 7816) or the NFC contactless interface (ISO 14443).

See also

SELECT and GET MANUFACTURER CERTIFICATE commands for full details on the startup sequence and response fields.

Initialization

Right after the installation, the applet is not initialized and the user needs to send some parameters to use the card. The INIT command can only be executed on a fresh card; a reset is required if the card was already initialized. Many base parameters changes require a card reset (except PIN/PUK change).

The parameters are sent using “one shot encryption”: the AES key is directly the ECDH of the 2 keys (card and computer). In addition to the personal code number, one needs to generate a random common shared key for the card pairing, used later for a fully authenticated and secured channel.

Initialization parameters

Parameter

Size

Description

Owner Name

1 + 20B max

Length byte + up to 20 characters

Owner Email

1 + 60B max

Length byte + up to 60 characters

PIN

9B

4–9 digit number, padded with 0x00 to 9 bytes

PUK

12B

12 digits/letters/bytes

Pairing key

32B

Secure Channel first pairing key

The PIN must be 4 to 9 figure number characters ('0'–'9'). If the PIN is less than 9 bytes, it must be filled with 0x00 until 9 characters long.

The parameters sent are encrypted and the command payload is:

PubKey | IV | EncryptedParams

During initialization, three independent key derivation trees are prepared for secp256k1, secp256r1, and Ed25519 (EdDSA). Each tree maintains its own seed and derivation hierarchy, following BIP32 (for secp256k1), SLIP10 (for secp256r1), and SLIP10 (for Ed25519).

See also

INIT command for the full APDU specification.

Pairing

After the initialization, the card and the host must share a common secret to be used as an authenticated secure channel. This secret is required any time further to communicate with the card (using a secure channel). The registration of the first common secret (pairing key) is done during the init phase. There is 1 pairing key slot.

The user can use a common public pairing key and only use PIN for authentication. Otherwise, the user host needs to store its pairing key in a safe place. In the case the client would communicate with several cards, the user needs to associate the pairing key with the instance serial number of the card.

Note

If the user loses their pairing info, a stretched hash of the PUK (SHA256 applied 32 times) can be used as the pairing key (slot 0xFF).

See also

Reset

When the PUK code is sent into the RESET command, the card is reset. The reset PUK code is chosen during the initialization stage. The PUK reset code is a 12 characters long string, which allows a full reset of the card.

On top of this 12 characters secret, the reset is also secured by the user pairing key mechanism (if secret). That means that resetting a card requires, on top of the PUK, to know the pairing key to send the command encrypted. Still, the PUK can act as a pairing key on its own.

The reset command erases everything in the card, including all three key derivation trees (secp256k1, secp256r1, and Ed25519), and makes the card as it was before the initialization.

Important

The PUK tries are unlimited, but there is an internal loop hash that takes time inside the card for each try. Every 12 tries, a power cycle is required to perform new tries.

See also