diff --git a/lib/hd/private.js b/lib/hd/private.js
index 40164ff1..92f9a4e4 100644
--- a/lib/hd/private.js
+++ b/lib/hd/private.js
@@ -70,11 +70,11 @@ function HDPrivateKey(options) {
 HDPrivateKey.prototype.fromOptions = function fromOptions(options) {
   assert(options, 'No options for HD private key.');
   assert(util.isNumber(options.depth));
+  assert(options.depth >= 0 && options.depth <= 0xff);
   assert(Buffer.isBuffer(options.parentFingerPrint));
   assert(util.isNumber(options.childIndex));
   assert(Buffer.isBuffer(options.chainCode));
   assert(Buffer.isBuffer(options.privateKey));
-  assert(options.depth <= 0xff, 'Depth is too high.');
 
   if (options.network)
     this.network = Network.get(options.network);
@@ -179,15 +179,12 @@ HDPrivateKey.prototype.destroy = function destroy(pub) {
 HDPrivateKey.prototype.derive = function derive(index, hardened) {
   var bw, id, data, hash, left, right, key, child;
 
-  if (typeof index === 'string')
-    return this.derivePath(index);
+  assert(typeof index === 'number');
 
-  hardened = index >= common.HARDENED ? true : hardened;
-
-  if (index < common.HARDENED && hardened)
+  if (hardened && index < common.HARDENED)
     index += common.HARDENED;
 
-  if (!(index >= 0 && index < common.MAX_INDEX))
+  if (index < 0 || index >= common.MAX_INDEX)
     throw new Error('Index out of range.');
 
   if (this.depth >= 0xff)
@@ -201,7 +198,7 @@ HDPrivateKey.prototype.derive = function derive(index, hardened) {
 
   bw = new StaticWriter(37);
 
-  if (hardened) {
+  if (index >= common.HARDENED) {
     bw.writeU8(0);
     bw.writeBytes(this.privateKey);
     bw.writeU32BE(index);
@@ -422,8 +419,7 @@ HDPrivateKey.prototype.equal = function equal(obj) {
 HDPrivateKey.prototype.compare = function compare(key) {
   var cmp;
 
-  if (!HDPrivateKey.isHDPrivateKey(key))
-    return 1;
+  assert(HDPrivateKey.isHDPrivateKey(key));
 
   cmp = this.depth - key.depth;
 
@@ -471,7 +467,6 @@ HDPrivateKey.prototype.fromSeed = function fromSeed(seed, network) {
   }
 
   hash = crypto.hmac('sha512', seed, common.SEED_SALT);
-
   left = hash.slice(0, 32);
   right = hash.slice(32, 64);
 
@@ -609,7 +604,7 @@ HDPrivateKey.prototype.fromBase58 = function fromBase58(xkey, network) {
 /**
  * Inject properties from serialized data.
  * @private
- * @param {Buffer} raw
+ * @param {BufferReader} br
  * @param {(Network|NetworkType)?} network
  */
 
@@ -621,7 +616,7 @@ HDPrivateKey.prototype.fromReader = function fromReader(br, network) {
   this.parentFingerPrint = br.readBytes(4);
   this.childIndex = br.readU32BE();
   this.chainCode = br.readBytes(32);
-  br.readU8();
+  assert(br.readU8() === 0);
   this.privateKey = br.readBytes(32);
   this.publicKey = ec.publicKeyCreate(this.privateKey, true);
 
@@ -633,12 +628,12 @@ HDPrivateKey.prototype.fromReader = function fromReader(br, network) {
 /**
  * Inject properties from serialized data.
  * @private
- * @param {Buffer} raw
+ * @param {Buffer} data
  * @param {(Network|NetworkType)?} network
  */
 
-HDPrivateKey.prototype.fromRaw = function fromRaw(raw, network) {
-  return this.fromReader(new BufferReader(raw), network);
+HDPrivateKey.prototype.fromRaw = function fromRaw(data, network) {
+  return this.fromReader(new BufferReader(data), network);
 };
 
 /**
@@ -718,13 +713,13 @@ HDPrivateKey.fromReader = function fromReader(br, network) {
 
 /**
  * Instantiate key from serialized data.
- * @param {Buffer} raw
+ * @param {Buffer} data
  * @param {(Network|NetworkType)?} network
  * @returns {HDPrivateKey}
  */
 
-HDPrivateKey.fromRaw = function fromRaw(raw, network) {
-  return new HDPrivateKey().fromRaw(raw, network);
+HDPrivateKey.fromRaw = function fromRaw(data, network) {
+  return new HDPrivateKey().fromRaw(data, network);
 };
 
 /**
diff --git a/lib/hd/public.js b/lib/hd/public.js
index 9b782ca1..d4f8c167 100644
--- a/lib/hd/public.js
+++ b/lib/hd/public.js
@@ -64,6 +64,7 @@ function HDPublicKey(options) {
 HDPublicKey.prototype.fromOptions = function fromOptions(options) {
   assert(options, 'No options for HDPublicKey');
   assert(util.isNumber(options.depth));
+  assert(options.depth >= 0 && options.depth <= 0xff);
   assert(Buffer.isBuffer(options.parentFingerPrint));
   assert(util.isNumber(options.childIndex));
   assert(Buffer.isBuffer(options.chainCode));
@@ -152,11 +153,10 @@ HDPublicKey.prototype.destroy = function destroy() {
 HDPublicKey.prototype.derive = function derive(index, hardened) {
   var bw, id, data, hash, left, right, key, child;
 
-  if (typeof index === 'string')
-    return this.derivePath(index);
+  assert(typeof index === 'number');
 
   if (index >= common.HARDENED || hardened)
-    throw new Error('Index out of range.');
+    throw new Error('Cannot derive hardened.');
 
   if (index < 0)
     throw new Error('Index out of range.');
@@ -335,8 +335,7 @@ HDPublicKey.prototype.equal = function equal(obj) {
 HDPublicKey.prototype.compare = function compare(key) {
   var cmp;
 
-  if (!HDPublicKey.isHDPublicKey(key))
-    return 1;
+  assert(HDPublicKey.isHDPublicKey(key));
 
   cmp = this.depth - key.depth;
 
@@ -469,7 +468,7 @@ HDPublicKey.prototype.fromBase58 = function fromBase58(xkey, network) {
 /**
  * Inject properties from serialized data.
  * @private
- * @param {Buffer} raw
+ * @param {BufferReader} br
  * @param {(Network|NetworkType)?} network
  */
 
@@ -491,12 +490,12 @@ HDPublicKey.prototype.fromReader = function fromReader(br, network) {
 /**
  * Inject properties from serialized data.
  * @private
- * @param {Buffer} raw
+ * @param {Buffer} data
  * @param {(Network|NetworkType)?} network
  */
 
-HDPublicKey.prototype.fromRaw = function fromRaw(raw, network) {
-  return this.fromReader(new BufferReader(raw), network);
+HDPublicKey.prototype.fromRaw = function fromRaw(data, network) {
+  return this.fromReader(new BufferReader(data), network);
 };
 
 /**
@@ -575,7 +574,7 @@ HDPublicKey.fromReader = function fromReader(br, network) {
 
 /**
  * Instantiate key from serialized data.
- * @param {Buffer} raw
+ * @param {Buffer} data
  * @param {(Network|NetworkType)?} network
  * @returns {HDPublicKey}
  */
diff --git a/test/hd-test.js b/test/hd-test.js
index 6a4594e7..4c2f2ed9 100644
--- a/test/hd-test.js
+++ b/test/hd-test.js
@@ -107,7 +107,7 @@ describe('HD', function() {
         return;
 
       it('should derive ' + path + ' from master', function() {
-        var key = master.derive(path);
+        var key = master.derivePath(path);
         equal(key.toBase58(), kp.prv);
         equal(key.toPublic().toBase58(), kp.pub);
       });
diff --git a/test/wallet-test.js b/test/wallet-test.js
index be5c1f72..11bf291d 100644
--- a/test/wallet-test.js
+++ b/test/wallet-test.js
@@ -159,7 +159,7 @@ describe('Wallet', function() {
 
     script = Script.fromMultisig(1, 2, [
       w.account.receive.getPublicKey(),
-      k.derive('m/0/0').publicKey
+      k.derivePath('m/0/0').publicKey
     ]);
 
     // Input transaction (bare 1-of-2 multisig)