diff --git a/Sign.js b/Sign.js
new file mode 100644
index 000000000..24889dc56
--- /dev/null
+++ b/Sign.js
@@ -0,0 +1,133 @@
+
+function signOne(hash, addrStr, keys)
+{
+	var keyObj = keys[addrStr];
+	var rawPrivKey = new Buffer(keyObj.priv, 'hex');
+	var key = new KeyModule.Key();
+	key.private = rawPrivKey;
+	var signature = key.signSync(hash);
+
+	return signature;
+}
+
+function signTxIn(nIn, tx, txInputs, network, keys, scripts)
+{
+	// locate TX input needing a signature
+	var txin = tx.ins[nIn];
+	var scriptSig = txin.getScript();
+
+	// locate TX output, within txInputs
+	var txoutHash = txin.getOutpointHash();
+	if (!(txoutHash in txInputs))
+		throw new Error("signTxIn missing input hash");
+	var txFrom = txInputs[txoutHash];
+	var txoutIndex = txin.getOutpointIndex();
+	if (txFrom.outs.length >= txoutIndex)
+		throw new Error("signTxIn missing input index");
+	var txout = txFrom.outs[txoutIndex];
+	var scriptPubKey = txout.getScript();
+
+	// detect type of transaction, and extract useful elements
+	var txType = scriptPubKey.classify();
+	if (txType == TX_UNKNOWN)
+		throw new Error("unknown TX type");
+	var scriptData = scriptPubKey.capture();
+
+	// if P2SH, lookup the script
+	var subscriptRaw = undefined;
+	var subscript = undefined;
+	var subType = undefined;
+	var subData = undefined;
+	if (txType == TX_SCRIPTHASH) {
+		var addr = new Address(network.addressScript, scriptData[0]);
+		var addrStr = addr.toString();
+		if (!(addrStr in scripts))
+			throw new Error("unknown script hash address");
+
+		subscriptRaw = new Buffer(scripts[addrStr], 'hex');
+		subscript = new Script(subscriptRaw);
+		subType = subscript.classify();
+		if (subType == TX_UNKNOWN)
+			throw new Error("unknown subscript TX type");
+		subData = subscript.capture();
+	}
+
+	var hash = tx.hashForSignature(scriptPubKey, i, 0);
+
+	switch (txType) {
+	case TX_PUBKEY:
+		// already signed
+		if (scriptSig.chunks.length > 0)
+			return;
+
+		var pubkeyhash = util.sha256ripe160(scriptData[0]);
+		var addr = new Address(network.addressPubkey, pubkeyhash);
+		var addrStr = addr.toString();
+		if (!(addrStr in keys))
+			throw new Error("unknown pubkey");
+
+		var signature = signOne(hash, addrStr, keys);
+		scriptSig.writeBytes(signature);
+		break;
+
+	case TX_PUBKEYHASH:
+		// already signed
+		if (scriptSig.chunks.length > 0)
+			return;
+
+		var addr = new Address(network.addressPubkey, scriptData[0]);
+		var addrStr = addr.toString();
+		if (!(addrStr in keys))
+			throw new Error("unknown pubkey hash address");
+
+		var signature = signOne(hash, addrStr, keys);
+		scriptSig.writeBytes(signature);
+		scriptSig.writeBytes(key.public);
+		break;
+
+	case TX_SCRIPTHASH:
+		// already signed
+		if (scriptSig.chunks.length > 0)
+			return;
+
+		var addr = new Address(network.addressPubkey, subData[0]);
+		var addrStr = addr.toString();
+		if (!(addrStr in keys))
+			throw new Error("unknown script(pubkey hash) address");
+
+		var signature = signOne(hash, addrStr, keys);
+		scriptSig.writeBytes(signature);
+		scriptSig.writeBytes(key.public);
+		break;
+
+	case TX_MULTISIG:
+		while (scriptSig.chunks.length < scriptData.length) {
+			scriptSig.writeBytes(util.EMPTY_BUFFER);
+		}
+		for (var i = 0; i < scriptData.length; i++) {
+			// skip already signed
+			if (scriptSig.chunks[i].length > 0)
+				continue;
+
+			var pubkeyhash = util.sha256ripe160(scriptSig.chunks[i]);
+			var addr = new Address(network.addressPubkey, pubkeyhash);
+			var addrStr = addr.toString();
+			if (!(addrStr in keys))
+				continue;
+
+			var signature = signOne(hash, addrStr, keys);
+			scriptSig.chunks[i] = signature;
+		}
+		break;
+	}
+
+	if (txtype == TX_SCRIPTHASH)
+		scriptSig.writeBytes(subscriptRaw);
+}
+
+exports.Transaction = function Transaction(tx, txInputs, network, keys, scripts)
+{
+	for (var i = 0; i < tx.ins.length; i++)
+		signTxIn(i, tx, txInputs, network, keys, scripts);
+};
+
diff --git a/Transaction.js b/Transaction.js
index b96dcef5c..b4580b3b9 100644
--- a/Transaction.js
+++ b/Transaction.js
@@ -45,7 +45,7 @@ function spec(b) {
     return Buffer.concat([this.o, slen, this.s, qbuf]);
   };
 
-  TransactionIn.prototype.getOutpointHash = function getOutpointIndex() {
+  TransactionIn.prototype.getOutpointHash = function getOutpointHash() {
     if ("undefined" !== typeof this.o.outHashCache) {
       return this.o.outHashCache;
     }