Help with spending a custom script with Pay to Witness Script Hash

[dcale]

I have a working p2sh example and now I'm trying to replicate it with p2wsh. This is the working p2sh example (yes I'm sharing my test private keys):

import ECPairFactory from "ecpair";
import * as ecc from "tiny-secp256k1";
import * as bitcoin from "bitcoinjs-lib";
import { testnet } from "bitcoinjs-lib/src/networks";
import https from "https";

const NETWORK = testnet;
const ECPair = ECPairFactory(ecc);
bitcoin.initEccLib(ecc);

const keyPair = ECPair.fromWIF(
  "cW8RD4U8ovYDd5W6WxGEGsT7SxZfECBYZACziZzTDJEFd1YeXUkA",
  NETWORK
);

const pubkeyHex = keyPair.publicKey.toString("hex");

function createCustomWalletAddress(
  gateKeeperPublicKeyHex,
  targetRecipient
): string {
  const payloadScriptAsm = `${targetRecipient} OP_DROP ${gateKeeperPublicKeyHex} OP_CHECKSIG`;
  const payloadScript = bitcoin.script.fromASM(payloadScriptAsm);

  const { output, address, witness } = bitcoin.payments.p2sh({
    redeem: { output: payloadScript, network: NETWORK },
    network: NETWORK,
  });
  console.log("output", output);
  console.log("address", address);
  console.log("witness", witness);

  const tx = new bitcoin.Transaction();
  tx.version = 2;
  tx.addInput(
    Buffer.from(
      "73f407e46e019c7e8fc43fb77e809bb0e5d55a75849fd8986a4b785eb24017fc",
      "hex"
    ).reverse(),
    0
  );
  tx.addOutput(output!, 1500);

  const signatureHash = tx.hashForSignature(
    0,
    payloadScript,
    bitcoin.Transaction.SIGHASH_ALL
  );

  const redeemScriptSig = bitcoin.payments.p2sh({
    redeem: {
      input: bitcoin.script.compile([
        bitcoin.script.signature.encode(
          keyPair.sign(signatureHash),
          bitcoin.Transaction.SIGHASH_ALL
        ),
      ]),
      output: payloadScript,
    },
  }).input;
  console.log("redeemScriptSig", redeemScriptSig);
  tx.setInputScript(0, redeemScriptSig!);

  console.log("tx.ins", tx.ins);
  console.log("tx.outs", tx.outs);

  console.log("tx", tx.toHex());

  blockBookAPIGet(`/api/v2/sendtx/${tx.toHex()}`).then(console.log);

  return address!;
}

console.log(createCustomWalletAddress(pubkeyHex, "0011223344"));

Now I am able to successfully create a segwit address like so:

  const payloadScriptAsm = `${targetRecipient} OP_DROP ${gateKeeperPublicKeyHex} OP_CHECKSIG`;
  const payloadScript = bitcoin.script.fromASM(payloadScriptAsm);
  const txHash =  "0d68ef18fef2deacbd9efec230820b0a4bbd06f36c64fa740aef3a0614e3e60f"
  const inputNr = 1
  const { output, address, redeem } = bitcoin.payments.p2wsh({
    redeem: { output: payloadScript, network: NETWORK },
    network: NETWORK,
  });

But that's as far as I get, the bitcoin.Psbt does not seem to allow me pass custom script arguments (nor generate the signature I'm looking for). I'm looking for something like in my p2sh example were I could do:

  const redeemScriptSig = bitcoin.payments.p2sh({
    redeem: {
      input: bitcoin.script.compile([
        bitcoin.script.signature.encode(
          keyPair.sign(signatureHash),
          bitcoin.Transaction.SIGHASH_ALL
        ),
      ]),
      output: payloadScript,
    },
  }).input;
  console.log("redeemScriptSig", redeemScriptSig);

[junderw]

If you want to modify your existing code, replace:

1. hashForSignature with hashForWitnessV0 (and fill in the necessary extra data for the args (notably the input amount))
2. payments.p2sh with payments.p2wsh
3. }).input; with }).witness;
4. tx.setInputScript with tx.setWitness

And you should be good to go.

If you want to use Psbt, you need to write a finalizer.

If you're using TypeScript your IDE should help you with the arguments and return values required for the finalizer function that you need to pass in when finalizing.

[junderw]

(hashForWitnessV0 is correct for p2wsh, not hashForWitnessV1)

[dcale]

<3 wow thank you, it worked! Should've asked earlier :)