diff --git a/lib/bcoin/ec.js b/lib/bcoin/ec.js
index 594d42fb..40fa01de 100644
--- a/lib/bcoin/ec.js
+++ b/lib/bcoin/ec.js
@@ -46,10 +46,6 @@ ec.random = function random(size) {
   return new Buffer(elliptic.rand(size));
 };
 
-bn.prototype.toBuffer = function toBuffer(order, size) {
-  return new Buffer(this.toArray(order, size));
-};
-
 ec.verify = function verify(msg, sig, key, historical) {
   if (!Buffer.isBuffer(sig))
     return false;
@@ -170,8 +166,7 @@ function getLength(buf, p) {
 
 ec.isLowS = function isLowS(sig) {
   if (!sig.s) {
-    if (!Buffer.isBuffer(sig))
-      return false;
+    assert(Buffer.isBuffer(sig));
 
     try {
       sig = new bcoin.ecdsa.signature(sig);
diff --git a/lib/bcoin/hd.js b/lib/bcoin/hd.js
index 4b7add0b..f5959bc1 100644
--- a/lib/bcoin/hd.js
+++ b/lib/bcoin/hd.js
@@ -611,24 +611,24 @@ HDPrivateKey.prototype._unbuild = function _unbuild(xkey) {
   var off = 0;
   var hash;
 
-  data.version = utils.readU32BE(raw, off);
+  data.version = raw.slice(off, off + 4);
   off += 4;
-  data.depth = raw[off];
+  data.depth = raw.slice(off, off + 1);
   off += 1;
-  data.parentFingerPrint = utils.readU32BE(raw, off);
+  data.parentFingerPrint = raw.slice(off, off + 4);
   off += 4;
-  data.childIndex = utils.readU32BE(raw, off);
+  data.childIndex = raw.slice(off, off + 4);
   off += 4;
   data.chainCode = raw.slice(off, off + 32);
-  off += data.chainCode.length;
+  off += 32;
   off += 1; // nul byte
   data.privateKey = raw.slice(off, off + 32);
-  off += data.privateKey.length;
-  data.checksum = utils.readU32BE(raw, off);
+  off += 32;
+  data.checksum = raw.slice(off, off + 4);
   off += 4;
 
-  hash = utils.dsha256(raw.slice(0, -4));
-  if (data.checksum !== utils.readU32BE(hash, 0))
+  hash = utils.dsha256(raw.slice(0, -4)).slice(0, 4);
+  if (!utils.isEqual(data.checksum, hash))
     throw new Error('checksum mismatch');
 
   if (data.version === network.main.prefixes.xprivkey)
@@ -989,23 +989,23 @@ HDPublicKey.prototype._unbuild = function _unbuild(xkey) {
   var off = 0;
   var hash;
 
-  data.version = utils.readU32BE(raw, off);
+  data.version = raw.slice(off, off + 4);
   off += 4;
-  data.depth = raw[off];
+  data.depth = raw.slice(off, off + 1);
   off += 1;
-  data.parentFingerPrint = utils.readU32BE(raw, off);
+  data.parentFingerPrint = raw.slice(off, off + 4);
   off += 4;
-  data.childIndex = utils.readU32BE(raw, off);
+  data.childIndex = raw.slice(off, off + 4);
   off += 4;
   data.chainCode = raw.slice(off, off + 32);
-  off += data.chainCode.length;
+  off += 32;
   data.publicKey = raw.slice(off, off + 33);
-  off += data.publicKey.length;
-  data.checksum = utils.readU32BE(raw, off);
+  off += 33;
+  data.checksum = raw.slice(off, off + 4);
   off += 4;
 
-  hash = utils.dsha256(raw.slice(0, -4));
-  if (data.checksum !== utils.readU32BE(hash, 0))
+  hash = utils.dsha256(raw.slice(0, -4)).slice(0, 4);
+  if (!utils.isEqual(data.checksum, hash))
     throw new Error('checksum mismatch');
 
   if (data.version === network.main.prefixes.xpubkey)
@@ -1153,11 +1153,11 @@ HDPublicKey.prototype.deriveString = function deriveString(path) {
   };
 
   HD.prototype.sign = function sign() {
-    return this.key.sign.apply(this.key, arguments);
+    return bcoin.keypair.prototype.sign.apply(this, arguments);
   };
 
   HD.prototype.verify = function verify() {
-    return this.key.verify.apply(this.key, arguments);
+    return bcoin.keypair.prototype.verify.apply(this, arguments);
   };
 
   HD.prototype.compressed = true;
@@ -1167,10 +1167,6 @@ HDPrivateKey.prototype.toSecret = function toSecret() {
   return bcoin.keypair.toSecret.call(this);
 };
 
-HDPrivateKey.fromSecret = function fromSecret(privateKey) {
-  return bcoin.keypair.fromSecret(privateKey);
-};
-
 /**
  * Helpers
  */
diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index c3596fe7..89cfe454 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -1622,3 +1622,8 @@ utils.getMerkleRoot = function getMerkleRoot(items) {
 
   return tree[tree.length - 1];
 };
+
+// Hook into bn here to ensure we get a toBuffer() method.
+bn.prototype.toBuffer = function toBuffer(order, size) {
+  return new Buffer(this.toArray(order, size));
+};