diff --git a/lib/bcoin/hd.js b/lib/bcoin/hd.js
index bcac4a1a..8bb6c13a 100644
--- a/lib/bcoin/hd.js
+++ b/lib/bcoin/hd.js
@@ -87,7 +87,7 @@ var KeyPair = bcoin.keypair;
 var LRU = require('./lru');
 var BufferWriter = require('./writer');
 var BufferReader = require('./reader');
-var unorm = require('../../vendor/unorm');
+var unorm;
 
 /**
  * HD Mnemonic
@@ -137,8 +137,8 @@ Mnemonic.prototype.toSeed = function toSeed() {
     this.phrase = this.createMnemonic();
 
   this.seed = utils.pbkdf2(
-    unorm.nfkd(this.phrase),
-    unorm.nfkd('mnemonic' + this.passphrase),
+    nfkd(this.phrase),
+    nfkd('mnemonic' + this.passphrase),
     2048, 64);
 
   return this.seed;
@@ -337,6 +337,53 @@ HD.isExtended = function isExtended(data) {
     || HDPublicKey.isExtended(data);
 };
 
+/**
+ * Parse a derivation path and return an array of indexes.
+ * @see https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki
+ * @param {String} path
+ * @param {Number?} max - Max index.
+ * @returns {Number[]}
+ */
+
+HD.parsePath = function parsePath(path, max) {
+  var parts = path.split('/');
+  var root = parts.shift();
+  var indexes = [];
+  var i, hardened, index;
+
+  if (max == null)
+    max = constants.hd.MAX_INDEX;
+
+  if (constants.hd.PATH_ROOTS.indexOf(path) !== -1)
+    return indexes;
+
+  if (constants.hd.PATH_ROOTS.indexOf(root) === -1)
+    throw new Error('Bad path root.');
+
+  for (i = 0; i < parts.length; i++) {
+    index = parts[i];
+    hardened = index[index.length - 1] === '\'';
+
+    if (hardened)
+      index = index.slice(0, -1);
+
+    index = +index;
+
+    if (!(index >= 0))
+      throw new Error('Non-number path index.');
+
+    if (hardened)
+      index += constants.hd.HARDENED;
+
+    if (!(index >= 0 && index < max))
+      throw new Error('Index out of range.');
+
+    indexes.push(index);
+  }
+
+  return indexes;
+};
+
 /**
  * LRU cache to avoid deriving keys twice.
  * @type {LRU}
@@ -594,45 +641,6 @@ HDPrivateKey.isExtended = function isExtended(data) {
   return false;
 };
 
-/**
- * Parse a derivation path and return an array of indexes.
- * @see https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki
- * @returns {Number[]}
- */
-
-HDPrivateKey._getIndexes = function _getIndexes(path) {
-  var steps = path.split('/');
-  var root = steps.shift();
-  var indexes = [];
-  var i, step, hardened, index;
-
-  if (~constants.hd.PATH_ROOTS.indexOf(path))
-    return indexes;
-
-  if (!~constants.hd.PATH_ROOTS.indexOf(root))
-    return null;
-
-  for (i = 0; i < steps.length; i++) {
-    step = steps[i];
-    hardened = step[step.length - 1] === '\'';
-
-    if (hardened)
-      step = step.slice(0, -1);
-
-    if (!step || step[0] === '-')
-      return null;
-
-    index = +step;
-
-    if (hardened)
-      index += constants.hd.HARDENED;
-
-    indexes.push(index);
-  }
-
-  return indexes;
-};
-
 /**
  * Test whether a string is a valid path.
  * @param {String} path
@@ -640,21 +648,13 @@ HDPrivateKey._getIndexes = function _getIndexes(path) {
  * @returns {Boolean}
  */
 
-HDPrivateKey.isValidPath = function isValidPath(path, hardened) {
-  var indexes;
-
-  if (typeof path === 'string') {
-    indexes = HDPrivateKey._getIndexes(path);
-    return indexes !== null && indexes.every(HDPrivateKey.isValidPath);
+HDPrivateKey.isValidPath = function isValidPath(path) {
+  try {
+    HD.parsePath(path, constants.hd.MAX_INDEX);
+    return true;
+  } catch (e) {
+    return false;
   }
-
-  if (typeof path === 'number') {
-    if (path < constants.hd.HARDENED && hardened)
-      path += constants.hd.HARDENED;
-    return path >= 0 && path < constants.hd.MAX_INDEX;
-  }
-
-  return false;
 };
 
 /**
@@ -665,16 +665,14 @@ HDPrivateKey.isValidPath = function isValidPath(path, hardened) {
  */
 
 HDPrivateKey.prototype.derivePath = function derivePath(path) {
-  var indexes;
+  var indexes = HD.parsePath(path, constants.hd.MAX_INDEX);
+  var key = this;
+  var i;
 
-  if (!HDPrivateKey.isValidPath(path))
-    throw new Error('Invalid path.');
+  for (i = 0; i < indexes.length; i++)
+    key = key.derive(indexes[i]);
 
-  indexes = HDPrivateKey._getIndexes(path);
-
-  return indexes.reduce(function(prev, index) {
-    return prev.derive(index);
-  }, this);
+  return key;
 };
 
 /**
@@ -970,7 +968,10 @@ HDPrivateKey.fromJSON = function fromJSON(json, passphrase) {
  */
 
 HDPrivateKey.isHDPrivateKey = function isHDPrivateKey(obj) {
-  return obj && obj.xprivkey && typeof obj.derive === 'function';
+  return obj
+    && obj.hdPublicKey
+    && obj.hdPublicKey !== obj
+    && typeof obj.derive === 'function';
 };
 
 /**
@@ -1127,18 +1128,13 @@ HDPublicKey.prototype.isAccount44 = HDPrivateKey.prototype.isAccount44;
  * @returns {Boolean}
  */
 
-HDPublicKey.isValidPath = function isValidPath(arg) {
-  var indexes;
-
-  if (typeof arg === 'string') {
-    indexes = HDPrivateKey._getIndexes(arg);
-    return indexes !== null && indexes.every(HDPublicKey.isValidPath);
+HDPublicKey.isValidPath = function isValidPath(path) {
+  try {
+    HD.parsePath(path, constants.hd.HARDENED);
+    return true;
+  } catch (e) {
+    return false;
   }
-
-  if (typeof arg === 'number')
-    return arg >= 0 && arg < constants.hd.HARDENED;
-
-  return false;
 };
 
 /**
@@ -1150,19 +1146,14 @@ HDPublicKey.isValidPath = function isValidPath(arg) {
  */
 
 HDPublicKey.prototype.derivePath = function derivePath(path) {
-  var indexes;
+  var indexes = HD.parsePath(path, constants.hd.HARDENED);
+  var key = this;
+  var i;
 
-  if (path.indexOf('\'') !== -1)
-    throw new Error('Cannot derive hardened.');
+  for (i = 0; i < indexes.length; i++)
+    key = key.derive(indexes[i]);
 
-  if (!HDPublicKey.isValidPath(path))
-    throw new Error('Invalid path.');
-
-  indexes = HDPrivateKey._getIndexes(path);
-
-  return indexes.reduce(function(prev, index) {
-    return prev.derive(index);
-  }, this);
+  return key;
 };
 
 /**
@@ -1291,8 +1282,8 @@ HDPublicKey.fromBase58 = function fromBase58(xkey) {
 
 HDPublicKey.isHDPublicKey = function isHDPublicKey(obj) {
   return obj
-    && obj.xpubkey
-    && !obj.xprivkey
+    && obj.hdPublicKey
+    && obj.hdPublicKey === obj
     && typeof obj.derive === 'function';
 };
 
@@ -1352,10 +1343,28 @@ HDPublicKey.isHDPublicKey = function isHDPublicKey(obj) {
  * @returns {Base58String}
  */
 
-HDPrivateKey.prototype.toSecret = function toSecret() {
-  return KeyPair.prototype.toSecret.call(this);
+HDPrivateKey.prototype.toSecret = function toSecret(network) {
+  return KeyPair.prototype.toSecret.call(this, network);
 };
 
+/*
+ * Helpers
+ */
+
+function nfkd(str) {
+  if (str.normalize)
+    return str.normalize('NFKD');
+
+  if (!unorm)
+    unorm = require('../../vendor/unorm');
+
+  return unorm.nfkd(str);
+}
+
+/*
+ * Expose
+ */
+
 HD.Mnemonic = Mnemonic;
 HD.PrivateKey = HDPrivateKey;
 HD.PublicKey = HDPublicKey;
diff --git a/lib/bcoin/keypair.js b/lib/bcoin/keypair.js
index 3f0be566..e50dbfc6 100644
--- a/lib/bcoin/keypair.js
+++ b/lib/bcoin/keypair.js
@@ -128,8 +128,11 @@ KeyPair.prototype.getPublicKey = function getPublicKey(enc) {
  * @returns {Base58String}
  */
 
-KeyPair.prototype.toSecret = function toSecret() {
-  return KeyPair.toSecret(this.getPrivateKey(), this.compressed, this.network);
+KeyPair.prototype.toSecret = function toSecret(network) {
+  if (!network)
+    network = this.network;
+
+  return KeyPair.toSecret(this.getPrivateKey(), this.compressed, network);
 };
 
 /**
@@ -180,7 +183,7 @@ KeyPair.parseSecret = function parseSecret(secret) {
   privateKey = p.readBytes(32);
 
   if (p.left() > 4) {
-    assert(p.readU8() === 1);
+    assert(p.readU8() === 1, 'Bad compression flag.');
     compressed = true;
   }