bip322 0.0.10

Implements BIP322 generic message signing and verification
Documentation 
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use super::*;

pub const BIP322_TAG: &str = "BIP0322-signed-message";

/// Create the tagged message hash.
pub fn tagged_hash(tag: &str, message: impl AsRef<[u8]>) -> [u8; 32] {
  let tag_hash = Sha256::new().chain_update(tag).finalize();
  Sha256::new()
    .chain_update(tag_hash)
    .chain_update(tag_hash)
    .chain_update(message)
    .finalize()
    .into()
}

/// Create the `to_spend` transaction.
#[allow(clippy::result_large_err)]
pub fn create_to_spend(address: &Address, message: impl AsRef<[u8]>) -> Result<Transaction> {
  Ok(Transaction {
    version: Version(0),
    lock_time: LockTime::ZERO,
    input: vec![TxIn {
      previous_output: OutPoint {
        txid: "0000000000000000000000000000000000000000000000000000000000000000"
          .parse()
          .unwrap(),
        vout: 0xFFFFFFFF,
      },
      script_sig: script::Builder::new()
        .push_int(0)
        .push_slice::<&PushBytes>(
          tagged_hash(BIP322_TAG, message)
            .as_slice()
            .try_into()
            .unwrap(),
        )
        .into_script(),
      sequence: Sequence(0),
      witness: Witness::new(),
    }],
    output: vec![TxOut {
      value: Amount::from_sat(0),
      script_pubkey: address.script_pubkey(),
    }],
  })
}

/// Create the `to_sign` transaction.
#[allow(clippy::result_large_err)]
pub fn create_to_sign(to_spend: &Transaction, witness: Option<Witness>) -> Result<Psbt> {
  let inputs = vec![TxIn {
    previous_output: OutPoint {
      txid: to_spend.compute_txid(),
      vout: 0,
    },
    script_sig: ScriptBuf::new(),
    sequence: Sequence(0),
    witness: Witness::new(),
  }];

  let to_sign = Transaction {
    version: Version(0),
    lock_time: LockTime::ZERO,
    input: inputs,
    output: vec![TxOut {
      value: Amount::from_sat(0),
      script_pubkey: script::Builder::new()
        .push_opcode(opcodes::all::OP_RETURN)
        .into_script(),
    }],
  };

  let mut psbt = Psbt::from_unsigned_tx(to_sign).context(error::PsbtExtract)?;

  psbt.inputs[0].witness_utxo = Some(TxOut {
    value: Amount::from_sat(0),
    script_pubkey: to_spend.output[0].script_pubkey.clone(),
  });

  psbt.inputs[0].final_script_witness = witness;

  Ok(psbt)
}