fix hd privkey derivation.

lib/bcoin/hd.js

@@ -152,14 +152,13 @@ function HDPrivateKey(options) {
 
   this._build(data);
 
-  if (new bn(data.parentFingerPrint).cmpn(0) === 0) {
+  if (new bn(data.parentFingerPrint).cmpn(0) === 0)
     this.isMaster = true;
-    this.master = this;
+  else
-  } else {
+    this.isMaster = false;
-    this.master = options.master;
-  }
 
   this.isPrivate = true;
+  this.isPublic = false;
 }
 
 HDPrivateKey.prototype.scan44 = function scan44(options, txByAddress, callback) {
@@ -594,9 +593,10 @@ HDPrivateKey.prototype._build = function _build(data) {
   off += utils.copy(data.chainCode, sequence, off);
   off += utils.copy([0], sequence, off);
   off += utils.copy(data.privateKey, sequence, off);
+  assert(off === 78, off);
   checksum = utils.dsha256(sequence.slice(0, off)).slice(0, 4);
   off += utils.copy(checksum, sequence, off);
-  assert(off === 82);
+  assert(off === 82, off);
 
   xprivkey = utils.toBase58(sequence);
 
@@ -625,10 +625,8 @@ HDPrivateKey.prototype._build = function _build(data) {
     parentFingerPrint: this.parentFingerPrint,
     childIndex: this.childIndex,
     chainCode: this.chainCode,
-    privateKey: this.privateKey,
     checksum: this.checksum,
-    publicKey: this.publicKey,
+    publicKey: this.publicKey
-    master: this.master
   });
 
   this.xpubkey = this.hdpub.xpubkey;
@@ -653,17 +651,19 @@ HDPrivateKey.prototype.derive = function derive(index, hardened) {
   leftPart = new bn(hash.slice(0, 32));
   chainCode = hash.slice(32, 64);
 
-  privateKey = leftPart.add(new bn(this.privateKey)).mod(ec.curve.n).toArray();
+  privateKey = leftPart
+    .add(new bn(this.privateKey))
+    .mod(ec.curve.n)
+    .toArray('be', 32);
 
   return new HDPrivateKey({
-    version: null,
+    version: this.version,
     depth: new bn(this.depth).toNumber() + 1,
     parentFingerPrint: this.fingerPrint,
     childIndex: index,
     chainCode: chainCode,
     privateKey: privateKey,
-    checksum: null,
+    checksum: null
-    master: this.master
   });
 };
 
@@ -822,13 +822,12 @@ function HDPublicKey(options) {
 
   this._build(data);
 
-  if (new bn(data.parentFingerPrint).cmpn(0) === 0) {
+  if (new bn(data.parentFingerPrint).cmpn(0) === 0)
     this.isMaster = true;
-    this.master = this;
+  else
-  } else {
+    this.isMaster = false;
-    this.master = options.master;
-  }
 
+  this.isPrivate = false;
   this.isPublic = true;
 }
 
@@ -897,9 +896,10 @@ HDPublicKey.prototype._build = function _build(data) {
   off += utils.copy(data.childIndex, sequence, off);
   off += utils.copy(data.chainCode, sequence, off);
   off += utils.copy(data.publicKey, sequence, off);
+  assert(off === 78, off);
   checksum = utils.dsha256(sequence.slice(0, off)).slice(0, 4);
   off += utils.copy(checksum, sequence, off);
-  assert(off === 82);
+  assert(off === 82, off);
 
   if (!data.checksum || !data.checksum.length)
     data.checksum = checksum;
@@ -949,14 +949,13 @@ HDPublicKey.prototype.derive = function derive(index, hardened) {
   publicKey = bcoin.ecdsa.keyPair({ pub: point }).getPublic(true, 'array');
 
   return new HDPublicKey({
-    version: null,
+    version: this.version,
     depth: new bn(this.depth).toNumber() + 1,
     parentFingerPrint: this.fingerPrint,
     childIndex: index,
     chainCode: chainCode,
     publicKey: publicKey,
-    checksum: null,
+    checksum: null
-    master: this.master
   });
 };