some more optimization.

lib/bcoin/hd.js

@@ -722,7 +722,7 @@ HDPrivateKey.prototype._build = function _build(data) {
   this.hdPrivateKey = this;
 
   this.xpubkey = this.hdPublicKey.xpubkey;
-  this.key = bcoin.keypair({ privateKey: this.privateKey });
+  this.key = key;
 };
 
 HDPrivateKey.prototype.derive = function derive(index, hardened) {

lib/bcoin/keypair.js

@@ -28,18 +28,38 @@ function KeyPair(options) {
 
   if (!options.privateKey && !options.publicKey)
     throw new Error('No options for keypair');
-
-  this.key = bcoin.ecdsa.keyPair({
-    priv: options.privateKey,
-    pub: options.publicKey
-  });
-
-  this.privatePoint = this.key.getPrivate();
-  this.publicPoint = this.key.getPublic();
-  this.privateKey = this.getPrivateKey();
-  this.publicKey = this.getPublicKey();
 }
 
+KeyPair.prototype.__defineGetter__('key', function() {
+  if (!this._key) {
+    this._key = bcoin.ecdsa.keyPair({
+      priv: this.options.privateKey,
+      pub: this.options.publicKey
+    });
+  }
+  return this._key;
+});
+
+KeyPair.prototype.__defineGetter__('privatePoint', function() {
+  if (!this._privatePoint)
+    this._privatePoint = this.key.getPrivate();
+  return this._privatePoint;
+});
+
+KeyPair.prototype.__defineGetter__('publicPoint', function() {
+  if (!this._publicPoint)
+    this._publicPoint = this.key.getPublic();
+  return this._publicPoint;
+});
+
+KeyPair.prototype.__defineGetter__('privateKey', function() {
+  return this.getPrivateKey();
+});
+
+KeyPair.prototype.__defineGetter__('publicKey', function() {
+  return this.getPublicKey();
+});
+
 KeyPair.generate = function() {
   return new KeyPair(bcoin.ec.generate());
 };

lib/bcoin/wallet.js

@@ -355,8 +355,7 @@ Wallet.prototype.deriveAddress = function deriveAddress(change, index) {
   key = this.accountKey.derive(data.path);
 
   options = {
-    privateKey: key.privateKey,
+    key: key.key,
-    publicKey: key.publicKey,
     compressed: key.compressed,
     change: data.change,
     index: data.index,