# Application client

A small Python client for the Handshake Ledger app: enough to send APDUs,
build the records `SIGN_TX` streams, and decode what comes back.

- `handshake_command_sender.py`: APDU encoding and the `SIGN_TX` state machine
  (BEGIN / ADD_INPUT / ADD_OUTPUT / REVIEW / SIGN_INPUT), plus the status words
  from `src/main.rs::AppSW`.
- `handshake_transaction.py`: payload builders and the covenant item layouts
  from `shd/Sources/Covenants/CovenantData.swift`.
- `handshake_response_unpacker.py`: response decoding. Note the app returns
  **compressed** 33-byte public keys.
- `handshake_sighash.py`: an independent BIP-143-style sighash over BLAKE2b-256,
  written separately from the device's implementation so that a test failure
  means the two disagree rather than that one implementation is self-consistent.
- `py.typed`: marker for type checkers.