From 262e8f8401ed54b9592f4b08723795fcdd7f66b9 Mon Sep 17 00:00:00 2001
From: JP Richardson <jprichardson@gmail.com>
Date: Sat, 14 Jun 2014 12:49:52 -0500
Subject: [PATCH] lib/hdkey: refactored derive()

---
 lib/hdkey.js | 42 ++++++++++++++----------------------------
 1 file changed, 14 insertions(+), 28 deletions(-)

diff --git a/lib/hdkey.js b/lib/hdkey.js
index c72c811..d2ff8fa 100644
--- a/lib/hdkey.js
+++ b/lib/hdkey.js
@@ -70,29 +70,24 @@ Object.defineProperty(HDKey.prototype, 'publicOld', {
 
 
 HDKey.prototype.derive = function(path) {
-  var e = path.split('/')
-
-  // Special cases:
   if (path == 'm' || path == 'M' || path == 'm\'' || path == 'M\'')
     return this
 
+  var entries = path.split('/')
   var hkey = this
-  for (var i in e) {
-    var c = e[i]
-
-    if (i == 0 ) {
-      if (c != 'm') throw new Error('invalid path')
-      continue
+  entries.forEach(function(c, i) {
+    if (i == 0) {
+      assert(c, 'm', 'Invalid path')
+      return
     }
 
-    var usePrivate = (c.length > 1) && (c[c.length-1] == '\'')
-    var childIndex = parseInt(usePrivate ? c.slice(0, c.length - 1) : c) & (HARDENED_OFFSET - 1)
-
-    if (usePrivate)
-      childIndex += HARDENED_OFFSET
+    var hardened = (c.length > 1) && (c[c.length-1] == '\'')
+    var childIndex = parseInt(c, 10) //& (HARDENED_OFFSET - 1)
+    assert(childIndex < HARDENED_OFFSET, 'Invalid index')
+    if (hardened) childIndex += HARDENED_OFFSET
 
     hkey = hkey.deriveChild(childIndex)
-  }
+  })
 
   return hkey
 }
@@ -104,8 +99,7 @@ HDKey.prototype.deriveChild = function(index) {
 
   var data
 
-  // Hardened child
-  if (isHardened) {
+  if (isHardened) { // Hardened child
     assert(this.privateKey, 'Could not derive hardened child key')
 
     var pk = this.privateKey
@@ -113,19 +107,13 @@ HDKey.prototype.deriveChild = function(index) {
     pk = Buffer.concat([zb, pk])
 
     // data = 0x00 || ser256(kpar) || ser32(index)
-    data = Buffer.concat([pk, indexBuffer])
-
-  // Normal child
-  } else {
+    data = Buffer.concat([pk, indexBuffer])  
+  } else { // Normal child
     // data = serP(point(kpar)) || ser32(index)
     //      = serP(Kpar) || ser32(index)
-    data = Buffer.concat([
-      this.publicKey,
-      indexBuffer
-    ])
+    data = Buffer.concat([this.publicKey, indexBuffer])
   }
 
-  //var I = crypto.HmacSHA512(data, this.chaincode)
   var I = sha512.hmac(this.chainCode).finalize(data)
   var IL = I.slice(0, 32)
   var IR = I.slice(32)
@@ -143,8 +131,6 @@ HDKey.prototype.deriveChild = function(index) {
       return this.derive(index + 1)
     }
 
-    //hd.priv = new ECKey(ki.toBuffer(), true)
-    //hd.pub = hd.priv.publicPoint
     hd.privateKey = ki.toBuffer()
 
   // Public parent key -> public child key