bitcoin multisig transaction demo

bitcoinjs-lib.js

var bitcoin = require('bitcoinjs-lib') // 1.4.x ?


var privKeys = [
  'L2ALJznyt2croGHs8duBK2TZMB3Bc5ZpFZQSmR5QQUMPDDcUWeTw', // n2t8F1D41xy6f3d2B6DtjXRRsn8dgUzQ6C
  'L3gM5giJqPAJcWyD8eKv94d4QgqyzqrYeAA9DnuJe23FszsnqD1w', // mjgF67B4pyEHuGTLU5jS333EasUrZBaxMB
  'KwdYxYAbxntKvrMQtDHAamPT1pyuYkDRfAwESBqCGRdz9abQo3dW', // mwzPpNMFwLoJPXw2ez8mz6RrdYGaqZDind
  'L5LTWMRBt27dHde1mnvV1RzW1mxQuQBxpm2TvNHsMaNvAQKqKov2', // mt7K2ChnJSp96k93HYdC8B9oqUmqLyESpL
  'L4qQgxEbKJFJKans2UxFRzXisS7o3oBkyJGirAUgTxS9CfTo9Cd4', // mmvbfVqYrXdy1i4x9UzWc4PtgN7VjMNjeY
]
privKeys = privKeys.map(function(privKey) {
  return bitcoin.ECKey.fromWIF(privKey)
})
var pubKeys = privKeys.map(function(privKey) {
  return privKey.pub
})


// create multisig
var script = bitcoin.scripts.multisigOutput(2, [pubKeys[1], pubKeys[2], pubKeys[3]])

var txb1 = new bitcoin.TransactionBuilder()
txb1.addInput('9774024749b0104a98648641285cac4d518c9f824d9432d4ad67c1931028711b', 0)
txb1.addOutput(script, 990000)
txb1.sign(0, privKeys[0])

var tx1 = txb1.build()
console.log(tx1)
console.log(tx1.toHex()) // push tx to network

// spend multisig
var txb2 = new bitcoin.TransactionBuilder()
txb2.addInput(tx1.getId(), 0, bitcoin.Transaction.DEFAULT_SEQUENCE, script)
txb2.addOutput(pubKeys[4].getAddress(bitcoin.networks.testnet), 980000)
txb2.sign(0, privKeys[1])

var tx2 = txb2.buildIncomplete()

var txb3 = bitcoin.TransactionBuilder.fromTransaction(tx2)
txb3.prevOutScripts[0] = script
txb3.prevOutTypes[0] = 'multisig'
txb3.sign(0, privKeys[2])

var tx3 = txb3.build()
console.log(tx3)
console.log(tx3.toHex()) // push tx to network

bitcore.js

var _ = require('lodash')
var bitcore = require('bitcore') // 0.12.5

var network = bitcore.Networks.testnet
var totalKeys = 3
var requiredSignatures = 2

var rawPrivateKeys = [
  'cUTyK6kpESjzWRtvzb5KfenFB6PaGofwojkJMx68AQA6t2mQSKmV',
  'cVQS3PFi9t1XWXAH2fKs5xczmeXKb5v4ZbwJ8u7vPgK9Xjx9CDts',
  'cUoMsNvEeJGJpGwZNP3RRu9kYWHW4B2jTA3WPdnk9ZCMdtynJQDc'
]
// rawPrivateKeys = _.range(totalKeys).map(function () { return bitcore.PrivateKey(network).toWIF() })
var privateKeys = rawPrivateKeys.map(function (pk) { return bitcore.PrivateKey(pk) })
var publicKeys = privateKeys.map(function (pk) { return bitcore.PublicKey(pk) })

// multisig address
var address = bitcore.Address(publicKeys, requiredSignatures, network)

// get utxo from external source (chromanode, insight, blockr...)
var utxo = {
  txId: '9500bed37ae3deaec7357d67864a57e193b2f0c87906cd17f28a2b0218495879',
  outputIndex: 0,
  address: address.toString(),
  script: bitcore.Script(address).toHex(),
  satoshis: 129191578
}

// create tx
var txObj = bitcore.Transaction()
  .from(utxo, publicKeys, requiredSignatures)
  .to('n3E3sYxTwz4FCU3LdUnKiiG1PTcPC654Za', utxo.satoshis - 100000)
  .toObject()

// Alice sign tx
var sigAliceObj = bitcore.Transaction(txObj).getSignatures(privateKeys[0])[0]

// Bob sign tx
var sigBobObj = bitcore.Transaction(txObj).getSignatures(privateKeys[2])[0]

// apply Alice and Bob signatures
var tx = bitcore.Transaction(txObj)
  .applySignature(sigAliceObj)
  .applySignature(sigBobObj)

From this line : 23 (bitcoinjs-lib.js)

txb1.addInput('9774024749b0104a98648641285cac4d518c9f824d9432d4ad67c1931028711b', 0)

what is this : 9774024749b0104a98648641285cac4d518c9f824d9432d4ad67c1931028711b