diff --git a/Transaction.js b/Transaction.js
index e013d55..a8dbe45 100644
--- a/Transaction.js
+++ b/Transaction.js
@@ -294,15 +294,6 @@ Transaction.SIGHASH_NONE = SIGHASH_NONE;
 Transaction.SIGHASH_SINGLE = SIGHASH_SINGLE;
 Transaction.SIGHASH_ANYONECANPAY = SIGHASH_ANYONECANPAY;
 
-var oneBuffer = function() {
-  // bug present in bitcoind which must be also present in bitcore
-  // see https://bitcointalk.org/index.php?topic=260595
-  var ret = new Buffer(1);
-  ret.writeUInt8(1, 0);
-  return ret; // return 1 bug
-
-};
-
 var TransactionSignatureSerializer = function(txTo, scriptCode, nIn, nHashType) {
   this.txTo = txTo;
   this.scriptCode = scriptCode;
@@ -406,6 +397,16 @@ TransactionSignatureSerializer.prototype.buffer = function() {
   return this.bytes.buffer();
 };
 
+Transaction.Serializer = TransactionSignatureSerializer;
+
+var oneBuffer = function() {
+  // bug present in bitcoind which must be also present in bitcore
+  // see https://bitcointalk.org/index.php?topic=260595
+  var ret = new Buffer(1);
+  ret.writeUInt8(1, 0);
+  return ret; // return 1 bug
+};
+
 Transaction.prototype.hashForSignature =
   function hashForSignature(script, inIndex, hashType) {
 
@@ -428,108 +429,7 @@ Transaction.prototype.hashForSignature =
     // Append hashType
     var hashBuf = new Put().word32le(hashType).buffer();
     buffer = Buffer.concat([buffer, hashBuf]);
-    var bth = buffertools.toHex(buffer);
-    console.log('tx sig b ' + bth);
-    var expected = 'f40a750701b5788174aef79788716f96af779d7959147a0c2e0e5bfb6c2dba2df5b4b978940300000004005163acffffffff0445e6fd0200000000096aac536365526a526aa6546b000000000008acab656a6552535141a0fd010000000000c897ea030000000008526500ab526a6a631b39dba395e20496';
-    var rawtx = 'f40a750702af06efff3ea68e5d56e42bc41cdb8b6065c98f1221fe04a325a898cb61f3d7ee030000000363acacffffffffb5788174aef79788716f96af779d7959147a0c2e0e5bfb6c2dba2df5b4b97894030000000965510065535163ac6affffffff0445e6fd0200000000096aac536365526a526aa6546b000000000008acab656a6552535141a0fd010000000000c897ea030000000008526500ab526a6a631b39dba3';
-    console.log('expected '+expected);
-    for (var i=0; i<expected.length/2;i++) {
-      var byt = expected.substring(i*2, i*2+2);
-      var rbyt = bth.substring(i*2, i*2+2);
-      var interest = buffertools.toHex(this.serialize()) === rawtx;
-      if (interest) {
-        if (byt !== rbyt) throw new Error(byt +'!='+rbyt+' on pos '+i);
-        //console.log(byt+ ' OK at '+i); 
-      }
-    }
-
     return buffertools.reverse(util.twoSha256(buffer));
-
-
-
-    // In case concatenating two scripts ends up with two codeseparators,
-    // or an extra one at the end, this prevents all those possible
-    // incompatibilities.
-    script.findAndDelete(OP_CODESEPARATOR);
-
-    // Get mode portion of hashtype
-    var hashTypeMode = hashType & 0x1f;
-
-    // Generate modified transaction data for hash
-    var bytes = (new Put());
-    bytes.word32le(this.version);
-
-    // Serialize inputs
-    if (hashType & SIGHASH_ANYONECANPAY) {
-      // Blank out all inputs except current one, not recommended for open
-      // transactions.
-      bytes.varint(1);
-      bytes.put(this.ins[inIndex].o);
-      bytes.varint(script.buffer.length);
-      bytes.put(script.buffer);
-      bytes.word32le(this.ins[inIndex].q);
-    } else {
-      bytes.varint(this.ins.length);
-      for (var i = 0, l = this.ins.length; i < l; i++) {
-        var txin = this.ins[i];
-        bytes.put(this.ins[i].o);
-
-        // Current input's script gets set to the script to be signed, all others
-        // get blanked.
-        if (inIndex === i) {
-          bytes.varint(script.buffer.length);
-          bytes.put(script.buffer);
-        } else {
-          bytes.varint(0);
-        }
-
-        if (hashTypeMode === SIGHASH_NONE && inIndex !== i) {
-          bytes.word32le(0);
-        } else {
-          bytes.word32le(this.ins[i].q);
-        }
-      }
-    }
-
-    // Serialize outputs
-    if (hashTypeMode === SIGHASH_NONE) {
-      bytes.varint(0);
-    } else {
-      var outsLen;
-      var hashTypeMode = hashType & 0x1f;
-      if (hashTypeMode === SIGHASH_SINGLE) {
-        if (inIndex >= this.outs.length) {
-          return oneBuffer();
-        }
-        outsLen = inIndex + 1;
-      } else {
-        outsLen = this.outs.length;
-      }
-
-      // TODO: If hashTypeMode !== SIGHASH_SINGLE, we could memcpy this whole
-      //       section from the original transaction as is.
-      bytes.varint(outsLen);
-      for (var i = 0; i < outsLen; i++) {
-        if (hashTypeMode === SIGHASH_SINGLE && i !== inIndex) {
-          // Zero all outs except the one we want to keep
-          bytes.put(util.INT64_MAX);
-          bytes.varint(0);
-        } else {
-          bytes.put(this.outs[i].v);
-          bytes.varint(this.outs[i].s.length);
-          bytes.put(this.outs[i].s);
-        }
-      }
-    }
-
-    bytes.word32le(this.lock_time);
-
-    var buffer = bytes.buffer();
-
-    // Append hashType
-    buffer = Buffer.concat([buffer, new Buffer([parseInt(hashType), 0, 0, 0])]);
-
-    return util.twoSha256(buffer);
 };
 
 /**
diff --git a/test/test.sighash.js b/test/test.sighash.js
index 5fa7f87..77ad82b 100644
--- a/test/test.sighash.js
+++ b/test/test.sighash.js
@@ -95,111 +95,37 @@ var randomTx = function(single) {
 
 
 
+var oneBuffer = function() {
+  // bug present in bitcoind which must be also present in bitcore
+  // see https://bitcointalk.org/index.php?topic=260595
+  var ret = new Buffer(1);
+  ret.writeUInt8(1, 0);
+  return ret; // return 1 bug
+};
+
 
 
 var signatureHashOld = function(tx, script, inIndex, hashType) {
   if (+inIndex !== inIndex ||
     inIndex < 0 || inIndex >= tx.ins.length) {
-    throw new Error('Input index "' + inIndex + '" invalid or out of bounds ' +
-      '(' + tx.ins.length + ' inputs)');
+    return oneBuffer();
   }
-
-  // Clone transaction
-  var txTmp = new Transaction();
-  tx.ins.forEach(function(txin) {
-    txTmp.ins.push(new Transaction.In(txin));
-  });
-  tx.outs.forEach(function(txout) {
-    txTmp.outs.push(new Transaction.Out(txout));
-  });
-  txTmp.version = tx.version;
-  txTmp.lock_time = tx.lock_time;
-
-  // In case concatenating two scripts ends up with two codeseparators,
-  // or an extra one at the end, this prevents all those possible
-  // incompatibilities.
-  script.findAndDelete(Opcode.map.OP_CODESEPARATOR);
-
-  // Get mode portion of hashtype
+  // Check for invalid use of SIGHASH_SINGLE
   var hashTypeMode = hashType & 0x1f;
-
-  // Generate modified transaction data for hash
-  var bytes = (new Put());
-  bytes.word32le(tx.version);
-
-  // Serialize inputs
-  if (hashType & Transaction.SIGHASH_ANYONECANPAY) {
-    // Blank out all inputs except current one, not recommended for open
-    // transactions.
-    bytes.varint(1);
-    bytes.put(tx.ins[inIndex].o);
-    bytes.varint(script.buffer.length);
-    bytes.put(script.buffer);
-    bytes.word32le(tx.ins[inIndex].q);
-  } else {
-    bytes.varint(tx.ins.length);
-    for (var i = 0, l = tx.ins.length; i < l; i++) {
-      var txin = tx.ins[i];
-      bytes.put(txin.o);
-
-      // Current input's script gets set to the script to be signed, all others
-      // get blanked.
-      if (inIndex === i) {
-        bytes.varint(script.buffer.length);
-        bytes.put(script.buffer);
-      } else {
-        bytes.varint(0);
-      }
-
-      if (hashTypeMode === Transaction.SIGHASH_NONE && inIndex !== i) {
-        bytes.word32le(0);
-      } else {
-        bytes.word32le(tx.ins[i].q);
-      }
+  if (hashTypeMode === Transaction.SIGHASH_SINGLE) {
+    if (inIndex >= tx.outs.length) {
+      return oneBuffer();
     }
   }
 
-  // Serialize outputs
-  if (hashTypeMode === Transaction.SIGHASH_NONE) {
-    bytes.varint(0);
-  } else {
-    var outsLen;
-    if (hashTypeMode === Transaction.SIGHASH_SINGLE) {
-      if (inIndex >= txTmp.outs.length) {
-        // bug present in bitcoind which must be also present in bitcore
-        // Transaction.hashForSignature(): SIGHASH_SINGLE 
-        // no corresponding txout found - out of bounds
-        var ret = new Buffer(1);
-        ret.writeUInt8(1, 0);
-        return ret; // return 1 bug
-      }
-      outsLen = inIndex + 1;
-    } else {
-      outsLen = tx.outs.length;
-    }
-
-    bytes.varint(outsLen);
-    for (var i = 0; i < outsLen; i++) {
-      if (hashTypeMode === Transaction.SIGHASH_SINGLE && i !== inIndex) {
-        // Zero all outs except the one we want to keep
-        bytes.put(util.INT64_MAX);
-        bytes.varint(0);
-      } else {
-        bytes.put(tx.outs[i].v);
-        bytes.varint(tx.outs[i].s.length);
-        bytes.put(tx.outs[i].s);
-      }
-    }
-  }
-
-  bytes.word32le(tx.lock_time);
-
-  var buffer = bytes.buffer();
-
+  // Wrapper to serialize only the necessary parts of the transaction being signed
+  var serializer = new Transaction.Serializer(tx, script, inIndex, hashType);
+  // Serialize
+  var buffer = serializer.buffer();
   // Append hashType
-  buffer = Buffer.concat([buffer, new Buffer([parseInt(hashType), 0, 0, 0])]);
-
-  return util.twoSha256(buffer);
+  var hashBuf = new Put().word32le(hashType).buffer();
+  buffer = Buffer.concat([buffer, hashBuf]);
+  return buffertools.reverse(util.twoSha256(buffer));
 };
 
 
@@ -211,7 +137,7 @@ var signatureHashOld = function(tx, script, inIndex, hashType) {
 
 describe('Transaction sighash (#hashForSignature)', function() {
   for (var i = 0; i < 250; i++) {
-    it.skip('should hash correctly random tx #' + (i + 1), function() {
+    it('should hash correctly random tx #' + (i + 1), function() {
       var tx = randomTx();
       var l = tx.ins.length;
       for (var i = 0; i < l; i++) {
@@ -237,7 +163,7 @@ describe('Transaction sighash (#hashForSignature)', function() {
       var ser_tx = buffertools.toHex(tx.serialize());
       ser_tx.should.equal(buffertools.toHex(raw_tx));
       var h = buffertools.toHex(tx.hashForSignature(scriptPubKey, input_index, hashType));
-      h.should.equal(sighash); // compare our output with bitcoind's
+      h.should.equal(sighash); // compare our output with bitcoind's output
     });
 
   });