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APDUSPEC.md

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Cosmos App - Ledger Nano S

General structure

The general structure of commands and responses is as follows:

Commands

Field Type Content Note
CLA byte (1) Application Identifier 0x55
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

Command definition

GET_VERSION

Command

Field Type Content Expected
CLA byte (1) Application Identifier 0x55
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
CLA 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
SW1-SW2 byte (2) Return code see list of return codes

INS_GET_ADDR_SECP256K1

Command

Field Type Content Expected
CLA byte (1) Application Identifier 0x55
INS byte (1) Instruction ID 0x04
P1 byte (1) Display address/path on device 0x00 No
0x01 Yes
P2 byte (1) Parameter 2 ignored
L byte (1) Bytes in payload (depends)
HRP_LEN byte(1) Bech32 HRP Length 1<=HRP_LEN<=83
HRP byte (HRP_LEN) Bech32 HRP
Path[0] byte (4) Derivation Path Data 44
Path[1] byte (4) Derivation Path Data 118
Path[2] byte (4) Derivation Path Data ?
Path[3] byte (4) Derivation Path Data ?
Path[4] byte (4) Derivation Path Data ?

First three items in the derivation path will be hardened automatically hardened

Response

Field Type Content Note
PK byte (33) Compressed Public Key
ADDR byte (65) Bech 32 addr
SW1-SW2 byte (2) Return code see list of return codes

SIGN_SECP256K1

Command

Field Type Content Expected
CLA byte (1) Application Identifier 0x55
INS byte (1) Instruction ID 0x02
P1 byte (1) Payload desc 0 = init
1 = add
2 = last
P2 byte (1) Transaction Format 0 = json
1 = textual
L byte (1) Bytes in payload (depends)

The first packet/chunk includes only the derivation path

All other packets/chunks should contain message to sign

First Packet

Field Type Content Expected
Path[0] byte (4) Derivation Path Data 44
Path[1] byte (4) Derivation Path Data 118
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
Message bytes... Message to Sign

Response

Field Type Content Note
SIG byte (variable) Signature
SW1-SW2 byte (2) Return code see list of return codes

The signature data is DER encoded. The returned bytes have the following structure.

0x30 <length of whole message> <0x02> <length of R> <R> 0x2 <length of S> <S>