create-testnet-tx.js

// Create a real Zcash testnet transaction
const { proposeTransaction, getSighash, appendSignature, finalizeAndExtract } = require('./dist/index.js');
const secp256k1 = require('secp256k1');
const crypto = require('crypto');

// CONFIGURATION - UPDATE THESE WITH YOUR TESTNET VALUES
const CONFIG = {
  // Input UTXO (from testnet faucet)
  utxo: {
    txid: 'YOUR_TXID_HERE', // Get from zcash-cli listunspent
    vout: 0,
    value: 10000000n, // Amount in zatoshis (0.1 ZEC = 10000000)
    scriptPubKey: Buffer.from('YOUR_SCRIPTPUBKEY_HEX', 'hex'), // From listunspent
  },

  // Private key for signing (32 bytes hex)
  privateKey: 'YOUR_PRIVATE_KEY_HEX', // DO NOT COMMIT THIS!

  // Destination address
  destination: {
    address: 'tmYOUR_DESTINATION_ADDRESS', // Testnet transparent address
    amount: 9990000n, // Send 0.0999 ZEC (leaving 10000 for fee)
  }
};

async function createTestnetTransaction() {
  console.log('🔧 Creating Zcash Testnet Transaction\n');

  // Validate configuration
  if (CONFIG.utxo.txid === 'YOUR_TXID_HERE') {
    console.error('❌ ERROR: Please update CONFIG in create-testnet-tx.js with your testnet values');
    console.log('\n📝 Steps:');
    console.log('1. Get testnet ZEC from faucet: https://faucet.zecpages.com/');
    console.log('2. Run: zcash-cli -testnet listunspent');
    console.log('3. Update CONFIG.utxo with your UTXO details');
    console.log('4. Update CONFIG.privateKey with your private key');
    console.log('5. Update CONFIG.destination.address');
    process.exit(1);
  }

  try {
    // Prepare inputs
    const inputs = [[
      {
        txid: CONFIG.utxo.txid,
        vout: CONFIG.utxo.vout,
        sequence: 0xFFFFFFFE, // Enable RBF
      },
      {
        value: CONFIG.utxo.value,
        scriptPubKey: CONFIG.utxo.scriptPubKey,
      }
    ]];

    // Prepare payment request
    const request = {
      payments: [{
        address: CONFIG.destination.address,
        amount: CONFIG.destination.amount,
      }]
    };

    console.log('📋 Transaction Details:');
    console.log('   Input:', CONFIG.utxo.txid.slice(0, 16) + '...', 'vout:', CONFIG.utxo.vout);
    console.log('   Amount:', CONFIG.utxo.value.toString(), 'zatoshis');
    console.log('   Send to:', CONFIG.destination.address);
    console.log('   Send amount:', CONFIG.destination.amount.toString(), 'zatoshis');
    console.log('   Fee: ~10000 zatoshis\n');

    // Step 1: Create PCZT
    console.log('1️⃣  Creating PCZT...');
    const pczt = await proposeTransaction(inputs, request);
    console.log('✅ PCZT created');

    // Step 2: Get sighash
    console.log('\n2️⃣  Computing sighash...');
    const sighash = await getSighash(pczt, 0);
    console.log('✅ Sighash:', Buffer.from(sighash.hash).toString('hex'));

    // Step 3: Sign with private key
    console.log('\n3️⃣  Signing transaction...');
    const privateKeyBuffer = Buffer.from(CONFIG.privateKey, 'hex');
    const messageHash = Buffer.from(sighash.hash);

    const sigObj = secp256k1.ecdsaSign(messageHash, privateKeyBuffer);

    // Encode to DER format + SIGHASH_ALL
    const derSig = secp256k1.signatureExport(sigObj.signature);
    const signature = Buffer.concat([derSig, Buffer.from([0x01])]); // Add SIGHASH_ALL

    console.log('✅ Signature created:', signature.toString('hex').slice(0, 32) + '...');

    // Step 4: Append signature
    console.log('\n4️⃣  Appending signature to PCZT...');
    const signedPczt = await appendSignature(pczt, 0, signature);
    console.log('✅ Signature appended');

    // Step 5: Finalize
    console.log('\n5️⃣  Finalizing transaction...');
    const txBytes = await finalizeAndExtract(signedPczt);
    const txHex = Buffer.from(txBytes).toString('hex');
    console.log('✅ Transaction finalized!');
    console.log('   Size:', txBytes.length, 'bytes');

    console.log('\n📤 Raw Transaction (hex):');
    console.log(txHex);

    console.log('\n🚀 Next Steps:');
    console.log('1. Broadcast with: zcash-cli -testnet sendrawtransaction', txHex.slice(0, 32) + '...');
    console.log('2. Or use block explorer to broadcast');
    console.log('3. Wait for confirmation and note the TXID');
    console.log('\n💡 Save this TXID for bounty submission!');

  } catch (error) {
    console.error('\n❌ Error:', error.message);
    console.error(error.stack);
    process.exit(1);
  }
}

// Run
createTestnetTransaction().catch(console.error);