diff --git a/lib/BIP32.js b/lib/BIP32.js
index 569828b..06c7770 100644
--- a/lib/BIP32.js
+++ b/lib/BIP32.js
@@ -136,28 +136,20 @@ 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 +171,21 @@ 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) {