Native P2WSH over P2SH | P2SH-P2WSH

Question

I'm in the process of attempting to generate a transaction using the Python Bitcoin Utils library. that involves P2WSH-over-P2SH (P2SH-P2WSH). My activity is on the regtest network. Below is the code snippet and address that I've prepared.

txin_redeemScript = Script([
    'OP_2',
    private_key1.get_public_key().to_hex(),
    private_key2.get_public_key().to_hex(),
    'OP_2',
    'OP_CHECKMULTISIG'
])
script_bytes = txin_redeemScript.to_bytes()
hashsha256 = hashlib.sha256(script_bytes).digest()
hashsha256 = hexlify(hashsha256).decode('utf-8')

txin_scriptPubKey = Script(['OP_0', hashsha256])
txin_p2wsh_address = P2shAddress.from_script(txin_scriptPubKey)

This address is where I intend to send the coins, and this is the transaction I'm forming:

p2pkh_addr = P2pkhAddress('n4bkvTyU1dVdzsrhWBqBw8fEMbHjJvtmJR')
txout = TxOutput(to_satoshis(amount_to_send), p2pkh_addr.to_script_pub_key())
tx = Transaction(inputs=p2sh_utxo, outputs=[txout], has_segwit=False)

This is the transaction and raw transaction ID

[{'address': '2N4vHiXTCCVMt4TYimTGXRCySzNLXkdiPyH', 'category': 'send', 'amount': Decimal('-0.10000000'), 'vout': 1, 'fee': Decimal('-0.00001430'), 'confirmations': 0, 'trusted': True, 'txid': 'f5f9c98b0c7b0731cba11f5a1b0494a62d2a2de5c09aaf3ac37fa56d48c271bd', 'wtxid': 'bed63897ca9c23ee891a9752b143ee063bf9aa97c813c5a455210a5f8437be6a', 'walletconflicts': [], 'time': 1693271904, 'timereceived': 1693271904, 'bip125-replaceable': 'yes', 'abandoned': False}]

0200000001bd71c2486da57fc33aaf9ac0e52d2a2da694041b5a1fa1cb31077b0c8bc9f9f50100000000ffffffff015f5d9800000000001976a914fd337ad3bf81e086d96a68e1f8d6a0a510f8c24a88ac00000000

The following code is utilized to sign the transaction:

for tx_idx, txin in enumerate(p2sh_utxo):
    sig1 = sk1.sign_input(tx, tx_idx, txin_redeemScript)
    sig2 = sk2.sign_input(tx, tx_idx, txin_redeemScript)
    unlocking_script = Script(['OP_0', txin_redeemScript.to_hex()])
    txin.script_sig = unlocking_script

    witness_data = [b'','OP_0', sig1, sig2]
    tx.witnesses.append(TxWitnessInput(witness_data))

The mempool acceptance test is failing with the error 'reject-reason': 'mandatory-script-verify-flag-failed (Script evaluated without error but finished with a false/empty top stack element)'}

My familiarity with bitcoin programming is limited, and I've been unable to locate any sample code or references concerning P2WSH over P2SH. Despite searching various online resources, I have yet to find any explanations on how the spending process operates. Any help would be appreciated.

You can find the complete code here

Answer 1

Construction of transaction to send to a P2SH(P2WSH) UTXO follows:

from bitcoinutils.keys import P2shAddress, PrivateKey
from bitcoinutils.script import Script
from bitcoinutils.setup import setup
from bitcoinutils.hdwallet import HDWallet
from bitcoinutils.transactions import Transaction, TxInput, TxOutput

setup("testnet")

#
# Send from a P2PKH UTXO and send to P2SH(P2WSH(P2PK))
# Change back to the same address (not recommended for privacy reasons)
#

xprivkey = (
    "tprv8ZgxMBicQKsPdQR9RuHpGGxSnNq8Jr3X4WnT6Nf2eq7FajuXyBep5KWYpYEixxx5XdTm1N"
    "tpe84f3cVcF7mZZ7mPkntaFXLGJD2tS7YJkWU"
)
path = "m/86'/1'/0'/0/1"
hdw = HDWallet(xprivkey, path)
from_priv = hdw.get_private_key()
from_pub = from_priv.get_public_key()
from_addr = from_pub.get_address()
print("From address:", from_addr.to_string())

hdw.from_path("m/86'/1'/0'/0/20")
to_priv = hdw.get_private_key()
to_pub = to_priv.get_public_key()

witness_script = Script([to_pub.to_hex(), "OP_CHECKSIG"])
p2sh_redeem_script = witness_script.to_p2wsh_script_pub_key()  # maybe to_p2sh_...

p2sh_address = P2shAddress.from_script(p2sh_redeem_script)
print("To address:", p2sh_address.to_string())

# UTXO's info
txid = "d4616b3050d2a0fac4783cd9a8c727aafa7b1374098d049e91ecc66d655e79e7"
vout = 0

txin = TxInput(txid, vout)
txout = TxOutput(5000, p2sh_redeem_script.to_p2sh_script_pub_key())
txout_change = TxOutput(1530000, from_addr.to_script_pub_key())
tx = Transaction([txin], [txout, txout_change])

sig = from_priv.sign_input(tx, 0, from_addr.to_script_pub_key())

txin.script_sig = Script([sig, from_pub.to_hex()])

signed_tx = tx.serialize()

print(signed_tx)

Construction of transaction to spend from a P2SH(P2WSH) UTXO follows:

from bitcoinutils.keys import P2shAddress, PrivateKey
from bitcoinutils.script import Script
from bitcoinutils.setup import setup
from bitcoinutils.hdwallet import HDWallet
from bitcoinutils.transactions import Transaction, TxInput, TxOutput, TxWitnessInput

setup("testnet")

#
# Send from a P2SH(P2WSH(P2PK)) UTXO to a P2PKH UTXO
#

xprivkey = (
    "tprv8ZgxMBicQKsPdQR9RuHpGGxSnNq8Jr3X4WnT6Nf2eq7FajuXyBep5KWYpYEixxx5XdTm1N"
    "tpe84f3cVcF7mZZ7mPkntaFXLGJD2tS7YJkWU"
)
path = "m/86'/1'/0'/0/20"
hdw = HDWallet(xprivkey, path)
from_priv = hdw.get_private_key()
print(from_priv.to_wif())
from_pub = from_priv.get_public_key()
from_addr = from_pub.get_address()

witness_script = Script([from_pub.to_hex(), "OP_CHECKSIG"])
p2sh_redeem_script = witness_script.to_p2wsh_script_pub_key()
print("From address:", P2shAddress.from_script(p2sh_redeem_script).to_string())

hdw.from_path("m/86'/1'/0'/0/25")
to_priv = hdw.get_private_key()
to_address = to_priv.get_public_key().get_address()
print("To address:", to_address.to_string())

# UTXO's info
txid = "217f123726bd8ace101afd705ae31384fd818fce17c8e00ce6fc0d24c0364355"
vout = 0
amount = 5000

txin = TxInput(txid, vout)
txout = TxOutput(3000, to_address.to_script_pub_key())
tx = Transaction([txin], [txout], has_segwit=True)

sig = from_priv.sign_segwit_input(tx, 0, witness_script, amount)

txin.script_sig = Script([p2sh_redeem_script.to_hex()])
tx.witnesses.append(TxWitnessInput([sig, witness_script.to_hex()]))

signed_tx = tx.serialize()

print(signed_tx)

See also: https://github.com/karask/python-bitcoin-utils/blob/master/examples/send_to_p2sh_p2wsh_p2pk_address.py

and

https://github.com/karask/python-bitcoin-utils/blob/master/examples/spend_from_p2sh_p2wsh_p2pk_address.py