APDU protocol description
This document aims to provide a description of the APDU protocol supported by the app, explaining what each instruction does, the expected parameters and return values
General Structure
The general structure of a reqeuest and response is as follows:
Request / Command
| Field | Type | Content | Note |
|---|
| CLA | byte (1) | Application Identifier | 0xFF, To be determined |
| INS | byte (1) | Instruction ID | |
| P1 | byte (1) | Parameter 1 | |
| P2 | byte (1) | Parameter 2 | |
| L | byte (1) | Bytes in payload | |
| PAYLOAD | byte (L) | Payload | |
Response
| Field | Type | Content | Note |
|---|
| ANSWER | byte (?) | Answer | depends on the command |
| SW1-SW2 | byte (2) | Return code | see list of return codes |
Return codes
| Return code | Description |
|---|
| 0x6400 | Execution Error |
| 0x6982 | Empty buffer |
| 0x6983 | Output buffer too small |
| 0x6986 | Command not allowed |
| 0x6D00 | INS not supported |
| 0x6E00 | CLA not supported |
| 0x6F00 | Unknown |
| 0x9000 | Success |
Commands definitions
GetVersion
This command will return the app version
Command
| Field | Type | Content | Expected |
|---|
| CLA | byte (1) | Application Identifier | |
| INS | byte (1) | Instruction ID | 0x00 |
| P1 | byte (1) | Parameter 1 | ignored |
| P2 | byte (1) | Parameter 2 | ignored |
| L | byte (1) | Bytes in payload | 0 |
Response
| Field | Type | Content | Note |
|---|
| TEST | byte (1) | Test Mode | 0xFF means test mode is enabled |
| MAJOR | byte (1) | Version Major | |
| MINOR | byte (1) | Version Minor | |
| PATCH | byte (1) | Version Patch | |
| LOCKED | byte (1) | Device is locked | |
| TARGET ID | byte (4) | Target ID | |
| SW1-SW2 | byte (2) | Return code | see list of return codes |
GetAddress
This command returns the public key corresponding to the secret key found at the given bip32 path, see below.
Command
| Field | Type | Content | Expected |
|---|
| CLA | byte (1) | Application Identifier | |
| INS | byte (1) | Instruction ID | 0x01 |
| P1 | byte (1) | Request User confirmation | No = 0 |
| P2 | byte (1) | ignored | |
| L | byte (1) | Bytes in payload | (depends) |
| PathN | byte (1) | Number of path components | ? (typically 4) |
| Path[0] | byte (4) | Derivation Path Data | 0x80000A55 |
| Path[1] | byte (4) | Derivation Path Data | 0xA2862AD3 |
| Path[2] | byte (4) | Derivation Path Data | ? |
| Path[3] | byte (4) | Derivation Path Data | ? |
| Path[4] | byte (4) | Derivation Path Data | ? |
Response
| Field | Type | Content | Note |
|---|
| PK_LEN | byte (1) | Bytes in PKEY | |
| PKEY | byte (??) | Public key bytes | |
| SW1-SW2 | byte (2) | Return code | see list of return codes |
Sign
This command will return a signature of the passed payload hashed with SHA256
Command
| Field | Type | Content | Expected |
|---|
| CLA | byte (1) | Application Identifier | |
| INS | byte (1) | Instruction ID | 0x02 |
| P1 | byte (1) | Payload desc | 0 = init |
| | | 1 = add |
| | | 2 = last |
| P2 | byte (1) | ignored | |
| L | byte (1) | Bytes in payload | (depends) |
The first packet/chunk includes only the derivation path
All other packets/chunks contain data chunks that are described below
First Packet
| Field | Type | Content | Expected |
|---|
| PathN | byte (1) | Number of path components | ? (typically 4) |
| Path[0] | byte (4) | Derivation Path Data | 0x80000A55 |
| Path[1] | byte (4) | Derivation Path Data | 0xA2862AD3 |
| Path[2] | byte (4) | Derivation Path Data | ? |
| Path[3] | byte (4) | Derivation Path Data | ? |
| Path[4] | byte (4) | Derivation Path Data | ? |
Other Chunks/Packets
| Field | Type | Content | Expected |
|---|
| Data | bytes... | Message | |
Data is defined as:
| Field | Type | Content | Expected |
|---|
| Message | bytes.. | Data to sign | |
Response
| Field | Type | Content | Note |
|---|
| SIG_HASH | byte (32) | Signed hash | SHA256 hash used as signature message |
| SIG | byte (65) | Signature | RSV encoded signature |
| SW1-SW2 | byte (2) | Return code | see list of return codes |
