diff --git a/lib/BIP32.js b/lib/BIP32.js
index 569828b29..94a7602aa 100644
--- a/lib/BIP32.js
+++ b/lib/BIP32.js
@@ -10,6 +10,11 @@ var networks = require('../networks');
 var secp256k1_n = new bignum("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141", 16);
 var secp256k1_Gx = new bignum("79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798", 16);
 
+/*
+random new BIP32: new BIP32();
+from extended public or private key: new BIP32(str);
+new blank BIP32: new BIP32(null);
+*/
 var BIP32 = function(bytes) {
   if (typeof bytes == 'undefined' || bytes == 'mainnet' || bytes == 'livenet') {
     bytes = 'livenet';
@@ -46,7 +51,7 @@ var BIP32 = function(bytes) {
     }
   }
 
-  if (bytes !== undefined) 
+  if (bytes !== undefined && bytes !== null) 
     this.initFromBytes(bytes);
 }
 
@@ -60,7 +65,7 @@ BIP32.seed = function(bytes, network) {
     return false; //need more entropy
   var hash = coinUtil.sha512hmac(bytes, new Buffer("Bitcoin seed"));
 
-  var bip32 = new BIP32();
+  var bip32 = new BIP32(null);
   bip32.depth = 0x00;
   bip32.parentFingerprint = new Buffer([0, 0, 0, 0]);
   bip32.childIndex = new Buffer([0, 0, 0, 0]);
@@ -136,28 +141,20 @@ BIP32.prototype.buildExtendedPublicKey = function() {
   }
 
   // Version
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([v >> 24])]);
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([(v >> 16) & 0xff])]);
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([(v >> 8) & 0xff])]);
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([v & 0xff])]);
-
-  // Depth
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([this.depth])]);
-
-  // Parent fingerprint
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, this.parentFingerprint]);
-
-  // Child index
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([this.childIndex >>> 24])]);
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([(this.childIndex >>> 16) & 0xff])]);
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([(this.childIndex >>> 8) & 0xff])]);
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, new Buffer([this.childIndex & 0xff])]);
-
-  // Chain code
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, this.chainCode]);
-
-  // Public key
-  this.extendedPublicKey = Buffer.concat([this.extendedPublicKey, this.eckey.public]);
+  this.extendedPublicKey = Buffer.concat([
+    new Buffer([v >> 24]),
+    new Buffer([(v >> 16) & 0xff]),
+    new Buffer([(v >> 8) & 0xff]),
+    new Buffer([v & 0xff]),
+    new Buffer([this.depth]),
+    this.parentFingerprint,
+    new Buffer([this.childIndex >>> 24]),
+    new Buffer([(this.childIndex >>> 16) & 0xff]),
+    new Buffer([(this.childIndex >>> 8) & 0xff]),
+    new Buffer([this.childIndex & 0xff]),
+    this.chainCode,
+    this.eckey.public
+  ]);
 }
 
 BIP32.prototype.extendedPublicKeyString = function(format) {
@@ -179,30 +176,21 @@ BIP32.prototype.buildExtendedPrivateKey = function() {
 
   var v = this.version;
 
-  // Version
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([v >> 24])]);
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([(v >> 16) & 0xff])]);
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([(v >> 8) & 0xff])]);
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([v & 0xff])]);
-
-  // Depth
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([this.depth])]);
-
-  // Parent fingerprint
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, this.parentFingerprint]);
-
-  // Child index
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([this.childIndex >>> 24])]);
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([(this.childIndex >>> 16) & 0xff])]);
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([(this.childIndex >>> 8) & 0xff])]);
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([this.childIndex & 0xff])]);
-
-  // Chain code
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, this.chainCode]);
-
-  // Private key
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, new Buffer([0])]);
-  this.extendedPrivateKey = Buffer.concat([this.extendedPrivateKey, this.eckey.private]);
+  this.extendedPrivateKey = Buffer.concat([
+    new Buffer([v >> 24]),
+    new Buffer([(v >> 16) & 0xff]),
+    new Buffer([(v >> 8) & 0xff]),
+    new Buffer([v & 0xff]),
+    new Buffer([this.depth]),
+    this.parentFingerprint,
+    new Buffer([this.childIndex >>> 24]),
+    new Buffer([(this.childIndex >>> 16) & 0xff]),
+    new Buffer([(this.childIndex >>> 8) & 0xff]),
+    new Buffer([this.childIndex & 0xff]),
+    this.chainCode,
+    new Buffer([0]),
+    this.eckey.private
+  ]);
 }
 
 BIP32.prototype.extendedPrivateKeyString = function(format) {
@@ -282,7 +270,7 @@ BIP32.prototype.deriveChild = function(i) {
     var priv = bignum.fromBuffer(this.eckey.private, {size: 32});
     var k = il.add(priv).mod(secp256k1_n);
 
-    ret = new BIP32();
+    ret = new BIP32(null);
     ret.chainCode = ir;
 
     ret.eckey = new Key();
@@ -293,12 +281,12 @@ BIP32.prototype.deriveChild = function(i) {
   } else {
     var data = Buffer.concat([this.eckey.public, ib]);
     var hash = coinUtil.sha512hmac(data, this.chainCode);
-    var il = bignum.fromBuffer(hash.slice(0, 32), {size: 32});
+    var il = hash.slice(0, 32);
     var ir = hash.slice(32, 64);
 
     // Ki = (IL + kpar)*G = IL*G + Kpar
     var ilGkey = new Key();
-    ilGkey.private = il.toBuffer({size: 32});
+    ilGkey.private = il;
     ilGkey.regenerateSync();
     var ilG = Point.fromKey(ilGkey);
     var oldkey = new Key();
@@ -306,7 +294,7 @@ BIP32.prototype.deriveChild = function(i) {
     var Kpar = Point.fromKey(oldkey);
     var newpub = Point.add(ilG, Kpar).toKey().public;
 
-    ret = new BIP32();
+    ret = new BIP32(null);
     ret.chainCode = new Buffer(ir);
 
     var eckey = new Key();