Ledger Application Code in C++

Ledger Application

• Source code forks off the ledger-boilerplate project
  • Source Code
• binary build
  • app.apdu
  • app.elf
  • app.hex
  • app.sha256

Source Code Explained

All Ledger transports must be sent with a byte prefix that defined what the payload type is. This is used to deserialize and display on the ledger device.

Please see for more information how Partisia Blockchain works:

• Address
• Transactions
• Deserializing

Address Derived

Partisia HD addresses are derived as follows:

• Path m/44'/3757'/0'/0/<idx>

  For Ledger idx will be 0

• The Private Key is derived from the HD Path, and the uncompressed Public Key is derived from the Private Key
• To keep compatibility we convert the 64 byte public key into 65 bytes by prefixing the public key with 0x04
• A sha256 hash is generated from the 65 bytes Public Key
• The first 20 bytes of the hash prepended by 0x00 to create a 21 byte Partisia Address

Transactions Explained

In Partisia blockchain a valid transaction signature is defined by the following steps:

• A Chain Id is appended to the end of a transaction payload

  Chain Id for Testnet is fixed at: [0, 0, 0, 27, 80, 97, 114, 116, 105, 115, 105, 97, 32, 66, 108, 111, 99, 107, 99, 104, 97, 105, 110, 32, 84, 101, 115, 116, 110, 101, 116] Chain Id for Mainnet is fixed at: [0, 0, 0, 19, 80, 97, 114, 116, 105, 115, 105, 97, 32, 66, 108, 111, 99, 107, 99, 104, 97, 105, 110]

• A sha256 hash is then generated from The transaction payload. This 32 byte hash is called the digest
• The private key is used to generate a canonical signature from the digest
• The Signature returned from the Ledger Device is in DER format. The ledger-mpc-app converts it into Partisia Signature format below.

Partisia Signatures

Partisia Signature are always 65 bytes and defined as follows:

Deserializing

Depending on the byte prefix the device, the ledger is set to deserialize in the following ways

UTF8 Message

Byte prefix 0x01 (mainnet) or 0x0B (testnet)

The payload must contain valid UTF8 bytes form byte range [1..]

Digest Hash

Byte prefix 0x03

The payload must be 33 bytes exactly with the first byte being 0x03

Transaction Payload

Byte prefix 0x02 (mainnet) or 0x0C (testnet)

Transaction must be formatted as follows:

Inner

24 bytes following the transaction type prefix

Header

25 bytes following the Inner

Transaction Payload

unknown bytes following the Header

Transaction MPC Transfer

There is a special check to see if the user is making a MPC transfer. If they are a more custom deserialization occurs and a more detailed display on the Ledger device is provided

Transaction Contract

For all other transactions, simply the Contract, fee, and payload are displayed

ledger-mpc-app

Partisia has developed a JS application that will interface with the Ledger App here:

• Source Code
• NPM

Running the App

To run the app and test all the functionality of the Ledger Device please do the following:

git clone git@gitlab.com:partisiablockchainapplications/ledger-mpc-app.git
cd ledger-mpc-app

# install dependencies
npm i

# add your MNEMONIC into a .env file
echo MNEMONIC="word1 word2 word3 ..." >> .env

# unlock and open ledger to Partisia App
npm run test

Example Interaction