signer.js

var BigInteger = require('bigi');
var bitcoin = require('bitcoinjs-lib');

module.exports = Sign;

function Sign(blockChain, template, keys) {
  var applySignature = function(to_sign, key){
    var b = new Buffer(to_sign, "hex");
    return key.sign(b).toDER().toString("hex");
  }

  var findKey = function(address) {
    for(var i = 0; i < keys.length; i++) {
      var keyAddr = keys[i].pub.getAddress(blockChain);
      if(address == keyAddr) {
        return keys[i];
      }
    }
  };

  for(var i = 0; i < template.inputs.length; i++) {
    var input = template.inputs[i];
    for(var j = 0; j < input.signatures.length; j++) {
      var signature = input.signatures[j];
      var key = findKey(signature.address);
      if(key == undefined) continue;
      var pub = key.pub.toHex();
      var sig = applySignature(signature.hash_to_sign, key);

      template.inputs[i].signatures[j]['public_key'] = pub;
      template.inputs[i].signatures[j]['signature'] = sig;
    }
  }
  return template;
};

Sign.keysFromStrings = function(kstrs) {
  var keys = [];
  kstrs.forEach(function(kstr) {
    if(/^[A-Z0-9]{64}$/i.test(kstr)) {
      var big = BigInteger.fromHex(kstr);
      keys.push(new bitcoin.ECKey(big, true));
      keys.push(new bitcoin.ECKey(big, false));
    } else {
      keys.push(bitcoin.ECKey.fromWIF(kstr));
    }
  });
  return keys;
};