checklocktimeverify – Unwitnessed P2SH spending using C++ libbitcoin

adminMay 2, 2024

I’m trying to use UTXO (Unwitness P2SH) using libbitcoin. I looked at the libbitcoin-system wiki documentation (https://github.com/libbitcoin/libbitcoin-system/wiki) but didn’t find a solution to my problem. Unfortunately, this page only provides guidance on nested SegWit P2SH spending.

The redemption script is as follows =>

<expiry time> OP_CHECKLOCKTIMEVERIFY OP_DROP OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG

Below is the C++ code I wrote =>

    int main() 
        wallet::ec_private privateKey1("secret for obvious reason");
        wallet::ec_public publicKey1 = privateKey1.to_public();
        data_chunk pubKey1 = to_chunk(publicKey1.point());

        short_hash KeyHash1 = bitcoin_short_hash(publicKey1.point());
        data_chunk locktime;
        extend_data(locktime, to_little_endian<uint32_t>(1713352486));

        script redeem_script = script(operation(locktime), operation(opcode(177)), operation(opcode(117)), operation(opcode(118)), operation(opcode(169)), operation(to_chunk(KeyHash1)), operation(opcode(136)), operation(opcode(172)));

        wallet::payment_address from_address1("p2sh-cltv-address");
        wallet::payment_address to_address1("p2pkh-legacy-address");

        hash_digest prev_txid1;
        decode_hash(prev_txid1, "prev-txid-in-hexadecimal-format");

        uint32_t input_index1 = 0;
        output_point vin1(prev_txid1, input_index1);

        //make Input
        input input1 = input();
        input1.set_previous_output(vin1);
        input1.set_sequence(0xfffffffe);

        uint64_t output_value1;
        decode_base10(output_value1, "0.00999770", 8);
        script output_script1 = script().to_pay_key_hash_pattern(to_address1.hash());
        output output1(output_value1, output_script1);
    
        // Get current time as a time_point
        auto now = std::chrono::system_clock::now();
        auto epoch = std::chrono::system_clock::to_time_t(now);
        auto unix_time = static_cast<uint32_t>(epoch);

        chain::transaction tx = chain::transaction();
        tx.set_version(2);
        tx.set_locktime(unix_time - 100000);
        tx.inputs().push_back(input1);
        tx.outputs().push_back(output1); 

        endorsement sig1; 
        if (script::create_endorsement(sig1, privateKey1.secret(), redeem_script, tx, 0u, sighash_algorithm::all, script_version::zero, 1000000))
        
            std::cout << "Signature: " << std::endl;
            std::cout << encode_base16(sig1) << "\n" << std::endl; 
        

        operation::list scriptSig1; 
        scriptSig1.push_back(operation(sig1));
        scriptSig1.push_back(operation(pubKey1));
        scriptSig1.push_back(operation(redeem_script.to_data(0)));
        script unlockingScript1(scriptSig1);
        std::cout << unlockingScript1.to_string(0) << "\n" << std:: endl;

        //Make Signed TX
        tx.inputs()(0).set_script(unlockingScript1);
        std::cout << "Raw Transaction: " << std::endl;
        std::cout << encode_base16(tx.to_data(true, true)) << std::endl;
        return 0;

The broadcast of the generated raw transaction returned an error (the signature should be 0 for a failed CHECK(MULTI)SIG operation). This indicates a problem with the signature part. I’ve checked every detail (at least I think so), from the script to the values, but I can’t figure out exactly what’s wrong. Can someone help me?

adminMay 2, 2024