Data commands

GET CARD INFO / READ DATA

Request APDU (encrypted)

CLA	INS	P1	P2	LC	Data
0x80	0xFA	Mode	Selector	—	None (or MAC only)

Preconditions: Secure Channel must be opened.

This command is the main data-retrieval interface of the card. Depending on the P1/P2 combination, it returns card-level metadata, user key slot information, or arbitrary user data pages. It is used after establishing a secure channel to inspect the card’s state and read back stored data.

P1/P2 combinations

P1	P2	Description
0x00	0x00	Card info (name, email, signature counter)
0x01-0x03	0x00	User key slot info (slot = P1)
0x00	0x01-0x03	User data pages (page = P2-1)

Response Data — P1=0, P2=0 (Card info)

When both P1 and P2 are zero, the card returns general identity and status information that was set during initialization with the INIT command. This is useful to display the cardholder’s name and email, check whether a key has been loaded, and monitor the signing activity through the signature counter.

Field	Size	Description
Key source info	1B	0x00 = no key; 'K' = single k1 pair; 'X' = extended k1 node; 'L' = external seed; 'S' = internal seed; 'D' = dual generation (see Seed management)
Name length	1B	Length of owner name
Name	0-20B	Owner name (as set during INIT)
Email length	1B	Length of owner email
Email	0-60B	Owner email (as set during INIT)
Signature counter	4B	Big-endian unsigned integer, incremented with each SIGN

Response Data — P1=1-3, P2=0 (User key slot)

When P1 is set to a slot index (1–3) with P2=0, the card returns the description and public key stored in that user key slot. These were originally written with the ADD USER KEY command. This requires PIN verification or a successful challenge-response beforehand.

Field	Size	Description
Info text	64B	User-provided description (fixed 64 bytes, as written by ADD USER KEY)
Public key	65B or 256B	EC R1 uncompressed (65B for slot 1/3) or RSA modulus (256B for slot 2)

Response Data — P2=1-3 (User data pages)

When P2 is set to a page index (1–3), the card returns the user data stored on that page. Pages are written with the WRITE DATA command and can hold up to 1200 bytes each, for a total of 3600 bytes of user-defined storage. This also requires PIN or challenge-response.

Field	Size	Description
User data	0-1200B	Data from the requested page

Status Words

SW	Description
0x9000	Success
0x6985	Secure channel not opened, or PIN/challenge not validated (required when P1>0 or P2>0)
0x6B00	Invalid P1/P2 combination or user data slot out of range

Note

When reading user data (P2>0), the command must be sent using the extended frame format header to receive data larger than 256 bytes. This is required by the ISO 7816 standard for long response payloads, even though the command frame itself is short.

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GET HISTORY

Request APDU (encrypted)

CLA	INS	P1	P2	LC	Data
0x80	0xFB	Slot	0x00	—	None (or MAC only)

Preconditions: Secure Channel opened, PIN or challenge-response validated.

The card maintains a circular history buffer of the last 149 signing operations. Each entry records the value of the signature counter at the time of signing and the 32-byte hash that was signed. This allows the host application to audit past transactions and verify that the card’s signing history matches expected blockchain activity.

The history slot number is provided in P1 (0 to 148). Slot 0 is the most recent entry.

Response Data — 36 bytes

Field	Size	Description
Signing counter	4B	Big-endian unsigned integer (counter value at time of signing)
Signed hash	32B	The 32-byte hash that was signed in this transaction

Status Words

SW	Description
0x9000	Success
0x6985	Secure channel not opened or PIN/challenge not performed
0x6A86	Invalid P1 (slot number out of range, must be 0–148)

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WRITE DATA

Request APDU (encrypted)

CLA	INS	P1	P2	LC	Data
0x80	0xFC	Mode	Page	var	MAC | Encrypted data

Preconditions: Secure Channel opened, PIN or challenge-response validated.

This command writes data to one of two storage areas: the user data pages (P1=0) or the custom bytes field (P1=1) that is returned in every SELECT response.

P1=0x00 — Write user data page

The card provides three pages of user-defined storage, each up to 1200 bytes, for a total of 3600 bytes. Pages are indexed by P2 (0 to 2) and must be written sequentially starting from page 0. The total user data length is computed as (P2 x 1200) + data_size, meaning that lower pages are considered fully written. The card verifies that previous pages were fully written before allowing a higher page to be written; otherwise it returns 0x6985.

For example, writing 200 bytes with P2=1 sets the total user data length to 1400 bytes (1200 for page 0 + 200 for page 1). The data can later be read back with the READ DATA command.

Field	Size	Description
User data	1-1200B	Data for this page

P1=0x01 — Write custom bytes

The custom bytes are 16 bytes of public data that are returned in every SELECT response. They can be used to provide personal hints about how to authenticate with the card, or to indicate what is stored inside. Take care that anyone who has physical access to the card can freely read these bytes.

By default, the custom bytes are set to 16 times 0x00.

Field	Size	Description
Custom bytes	16B	Public data returned in every SELECT response

Status Words

SW	Description
0x9000	Success
0x6985	PIN not validated, or previous pages not fully written (P1=0)
0x6700	Data length incorrect (>1200B for P1=0, or not exactly 16B for P1=1)
0x6A86	P1 not 0 nor 1, or P2 out of range (0–2)
0x6982	Data too large (outside secure channel frame capacity)

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GET PUBKEY

Request APDU (encrypted, or plaintext for pinless/clear read)

CLA	INS	P1	P2	LC	Data
0x80	0xC2	Derive	Export	var	MAC | Encrypted path (or empty)

Preconditions: Secure Channel opened, PIN or challenge-response validated (except pinless or clear public key read), key loaded.

This is the primary command for exporting public keys from the card. It can return the current key’s public key, the current derivation path, or a full BIP32 extended public key (xpub). It also supports on-the-fly derivation: the card computes the derived key from a given path without changing the card’s current derivation state, which is useful when the host needs a public key at a specific path for address generation without affecting the signing key.

P1 values

P1	Description
0x00	Current key k1
0x10	Current key r1
0x20	Current key Ed25519
0x01	Derive with k1 (OR with bits 7-6 for derivation source)
0x11	Derive with r1 (OR with bits 7-6 for derivation source)
0x21	Derive with Ed25519 (OR with bits 7-6 for derivation source + derive flag)

When using derivation (P1 LSB = 1), the source key can be selected by OR’ing P1 with the same derivation source flags as the DERIVE KEY command:

• Bits 7-6 = 00: derive from master

• Bits 7-6 = 01: derive from parent

• Bits 7-6 = 10: derive from current

P2 values

P2	Description
0x00	Read current derivation path
0x01	Read public key
0x02	Read extended public key (BIP32 xpub, P1 must be 0x00)

Request Data — P1=0x01/0x11/0x21 (derive, plaintext)

Field	Size	Description
Path elements	n x 4B	32-bit big-endian integers (1 to 8 levels)

When P1=0x00/0x10/0x20 with P2=0x00 or P2=0x01, no data is required.

Response Data — P2=0x00 (path)

Field	Size	Description
Path elements	n x 4B	Current derivation path as 32-bit big-endian integers

Response Data — P2=0x01 (public key)

Field	Size	Description
Public key	65B	EC uncompressed point (04 | X | Y)

Response Data — P2=0x02 (extended public key)

The xpub export must first be enabled using SET PUB EXPORT (P1=0). By default this capability is disabled from factory and after reset.

The response approximately matches the binary serialization format defined in the BIP32 standard. The difference is the fingerprint is given as 32 bytes (the full SHA-256 of the parent key) instead of the standard 4 bytes — the host must apply an external RIPEMD-160 computation and take the first 4 bytes to obtain the final BIP32 fingerprint (except for the master key, which is all zeros). There is no checksum, as the data is not Base58-encoded.

Field	Size	Description
Version	4B	BIP32 version bytes (default: BTC mainnet 0x0488B21E)
Depth	1B	Derivation depth
Fingerprint	32B	Parent key fingerprint (needs external RIPEMD-160 to get 4B)
Child number	4B	Child index
Chain code	32B	BIP32 chain code
Public key	33B	Compressed public key

The xpub can only be read at depth >= 3, in compliance with the BIP44 standard (the first 3 levels are hardened). The first 4 version bytes can be changed on the fly by the host to match the target blockchain; the card always sends BTC mainnet version bytes by default.

The extended public key is useful for wallet software to derive the last account address levels outside the card, manage address changes for each transaction, compute payment addresses in advance, and scan the address chain — all without requiring the card for each derivation.

Pinless and clear read modes

The public key can be read without PIN or secure channel in two scenarios:

1. Pinless path: If a pinless path was set with SET PINLESS PATH, and the current derivation path starts with the EIP-1581 prefix (m/43'/60'/1581'/...), the public key (P2=1) can be read without authentication. No derivation is allowed in this mode.

2. Clear public key read: If enabled via SET PUB EXPORT (P1=1), the current public key (P1=0/0x10, P2=1) can be read without PIN or secure channel. This is designed for point-of-sale systems that need to read the card’s payment address via NFC tap. No derivation is allowed in this mode.

Note

Using the derive option (P1 LSB=1), the card expects a path in the data. There is no way to derive with a null path within this command, so the master key cannot be read via live derivation. If the master public key is needed, set it as the current key with DERIVE KEY and then read the current key.

Status Words

SW	Description
0x9000	Success
0x6985	Not initialized, no key loaded, PIN not verified, or xpub export disabled
0x6A80	Malformed path
0x6A86	Invalid P1/P2 combination (e.g. P2=2 with P1 != 0)
0x6A88	Pinless path not set up, or clear read not allowed
0x6986	xpub requested at depth < 3
0x6983	Pinless query but current path not in the allowed range
0x6700	Current key requested with data present, or derive requested without data