cancel-msg

cancel-msg is a command-line utility for generating cancellation messages and signatures used in Charms Cast for canceling orders.

It provides tools to:

• Compute the exact cancellation message from a spell YAML file and a target UTXO ID.
• Sign messages using a BIP32 xpriv key.
• Compute Bitcoin signed message hashes.
• Convert P2WPKH addresses to legacy P2PKH addresses.

Requirements

• Rust 1.75+ (due to edition = "2021" and dependencies)
• Git (for charms-data dependency)

Installation

Clone the repository and install:

git clone https://github.com/your-org/cancel-msg.git  # or your repo
cd cancel-msg
cargo install --path .

Or build for release:

cargo build --release
./target/release/cancel-msg --help

Usage

cancel-msg <SUBCOMMAND>;

SUBCOMMANDS:
    sign      Sign a message with an xpriv key at a derivation path
    p2pkh     Convert a P2WPKH (Bech32) address to legacy P2PKH
    msghash   Compute the Bitcoin signed message hash for a message
    message   Compute the cancellation message for a spell UTXO

Use cancel-msg <SUBCOMMAND> --help for detailed flags.

sign

Signs a message using the provided xpriv and derivation path. Outputs the hex signature and instructions for adding to a spell's private_inputs.$CAST.edit_orders.cancel.

cancel-msg sign --message "utxo_hash outputs_hash" --xprv xprv... --path "m/86'/0'/0'/0/0"

message

Computes the cancellation message <utxo_id> <outputs_hash> from a spell YAML file, where outputs_hash is sha256d(tx_outs || coin_outs) for the outputs after the matching input UTXO.

Spell YAML structure (simplified):

• inputs: array with coins containing utxo_id matching <txid>:<vout>
• outs: map of outputs, including charms

cancel-msg message --spell path/to/spell.yaml --utxo-id txid:vout

msghash

cancel-msg msghash --message "your message"

p2pkh

cancel-msg p2pkh --address bc1q...

Workflow Example

1. Compute cancellation message:

   cancel-msg message --spell spell.yaml --utxo-id abc123def...456:2
   # Output: abc123def...456:2 0123456789abcdef...
   

2. Sign it:

   cancel-msg sign --message "abc123def...456:2 0123456789abcdef..." --xprv xprv... --path "m/..."
   

3. Add the signature 0: 304502... to your spell's private_inputs.$CAST.edit_orders.cancel.

Dependencies

• bitcoin-rs 0.32
• charms-data (git)
• clap, anyhow, serde_yaml, hex

License

MIT