Bitcoin

Spending – Learn how to spend non-standard scripts. Mainnet. 25,000 sat

I configured this code in Python using chatgpt. I worked really hard to learn, but I just can’t figure out how to spend without errors. All data required to create a raw transaction is provided below. I tried to use the first op_if condition. Post my code here. If someone can do it (and write it), it means I have to learn more and harder. Final transaction in hexadecimal format:

import hashlib
import ecdsa

def dSHA256(raw):
    return hashlib.sha256(hashlib.sha256(raw).digest()).digest()

def create_signature(private_key_hex, message):
    try:
        private_key_bytes = bytes.fromhex(private_key_hex)
        signing_key = ecdsa.SigningKey.from_string(private_key_bytes, curve=ecdsa.SECP256k1)
        signature = signing_key.sign_digest(message, sigencode=ecdsa.util.sigencode_der_canonize)
        return signature  # Do not append SIGHASH_ALL here
    except Exception as e:
        print(f"Error creating signature: e")
        return None

# Transaction version
version = (2).to_bytes(4, byteorder="little", signed=False)

# Input transaction (Outpoint)
txid = (bytes.fromhex("a1b1b291b076d90232a32638ad74f00ffd65cc355ca7e77b833ea0728ea07aab"))(::-1)
index = (164).to_bytes(4, byteorder="little", signed=False)
outpoint = txid + index

# Hashed outpoint
hashPrevOut = dSHA256(outpoint)

# Sequence
sequence = (0xfffffffe).to_bytes(4, byteorder="little", signed=False)  # Use a value less than 0xffffffff
hashSequence = dSHA256(sequence)

# Amount being spent
amount = (int(0.00025297 * 100000000)).to_bytes(8, byteorder="little", signed=True)

# Output to the specified address
value = (int(0.00005297 * 100000000)).to_bytes(8, byteorder="little", signed=True)
scriptPubKey_hex = "00206cadc53e5157ac4f0c8e98d0011fd8ccd14378b846b1b944478b3437324b992e"
scriptPubKey = bytes.fromhex(scriptPubKey_hex)
output = value + (len(scriptPubKey)).to_bytes(1, byteorder="little", signed=False) + scriptPubKey

# Hashed output
hashOutput = dSHA256(output)

# nLockTime
nLockTime = (820000).to_bytes(4, byteorder="little", signed=False)

# Sighash type
sighash = bytes.fromhex("01000000")

# Public and private keys
private_key_hex = "2BF933A3FC415D4BA19D07F3F5FF641E645D1BDF70CFE1674D54C0E66AAA681F"
verifying_key = ecdsa.SigningKey.from_string(bytes.fromhex(private_key_hex), curve=ecdsa.SECP256k1).get_verifying_key()
x_cor = bytes.fromhex(verifying_key.to_string().hex())(:32)
y_cor = bytes.fromhex(verifying_key.to_string().hex())(32:)
public_key = bytes.fromhex("02" + x_cor.hex()) if int.from_bytes(y_cor, byteorder="big", signed=True) % 2 == 0 else bytes.fromhex("03" + x_cor.hex())

# WitnessScript
witnessScript = bytes.fromhex("630320830cb17521024e24d2aff4e1c51eaf122e0e5a6dfe218f7b3b883d1eb537ce9a7e040b329ca5ac6703b0830cb17521030618b7d1a6747cb13bba78611646a8d08c3683e14a0d2a4483c877561e1416efac68")
scriptCode = witnessScript

# Transaction digest for signature
bip_143 = version + hashPrevOut + hashSequence + outpoint + scriptCode + amount + sequence + hashOutput + nLockTime + sighash
hashed_bip_143 = dSHA256(bip_143)

# Signature
signature = create_signature(private_key_hex, hashed_bip_143)

# Print the DER-encoded signature in hexadecimal form
print("Signature (DER-encoded) in hexadecimal form:", signature.hex())

# Append SIGHASH_ALL to the signature
signature += bytes.fromhex("01")

# Witness construction for the first branch of OP_IF
minimal_true = bytes.fromhex("01")  # Minimal push of true
witness = (
    bytes.fromhex("04")  # Number of elements in the witness
    + (len(signature)).to_bytes(1, byteorder="little", signed=False) + signature
    + (len(public_key)).to_bytes(1, byteorder="little", signed=False) + public_key
    + (len(minimal_true)).to_bytes(1, byteorder="little", signed=False) + minimal_true
    + (len(witnessScript)).to_bytes(1, byteorder="little", signed=False) + witnessScript
)

# Transaction input and output counts
tx_in_count = (1).to_bytes(1, byteorder="little", signed=False)
tx_out_count = (1).to_bytes(1, byteorder="little", signed=False)

# Marker and Flag for SegWit
marker = bytes.fromhex("00")
flag = bytes.fromhex("01")

# Final transaction assembly
final_tx = (
    version
    + marker
    + flag
    + tx_in_count
    + outpoint
    + (0).to_bytes(1, byteorder="little", signed=False)  # ScriptSig is empty for SegWit inputs
    + sequence
    + tx_out_count
    + output
    + witness
    + nLockTime
)

# Print the final transaction hex
print("Final transaction in hexadecimal form:", final_tx.hex())

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