diff --git a/src/Bitpay/Bitauth.php b/src/Bitpay/Bitauth.php
index 4a75706..fc47506 100644
--- a/src/Bitpay/Bitauth.php
+++ b/src/Bitpay/Bitauth.php
@@ -60,12 +60,11 @@ class Bitauth
     }
 
     /**
-     * @return Sin
+     * @return SinKey
      */
     public function getSinFromPublicKey(\Bitpay\PublicKey $publicKey)
     {
-        // TODO
-        //return Sin::fromPubKey($publicKey);
+        return $publicKey->getSin();
     }
 
     /**
@@ -78,80 +77,6 @@ class Bitauth
     public function sign($data, \Bitpay\PrivateKey $privateKey)
     {
         return $privateKey->sign($data);
-
-        //if (!ctype_xdigit($privateKey->getHex())) {
-        //    throw new \Exception('The private key must be in hex format.');
-        //}
-
-        //if (empty($data)) {
-        //    throw new \Exception('You did not provide any data to sign.');
-        //}
-
-        //$e = Util::decodeHex(hash('sha256', $data));
-
-        //do {
-        //    if (substr(strtolower($privateKey->getHex()), 0, 2) != '0x') {
-        //        $d = '0x'.$privateKey->getHex();
-        //    } else {
-        //        $d = $privateKey->getHex();
-        //    }
-
-        //    $k = SecureRandom::generateRandom(32);
-
-        //    $k_hex = '0x'.strtolower(bin2hex($k));
-        //    $n_hex = '0x'.Secp256k1::N;
-        //    $a_hex = '0x'.Secp256k1::A;
-        //    $p_hex = '0x'.Secp256k1::P;
-
-        //    $Gx = '0x'.substr(Secp256k1::G, 0, 62);
-        //    $Gy = '0x'.substr(Secp256k1::G, 64, 62);
-
-        //    $P = new Point($Gx, $Gy);
-
-        //    // Calculate a new curve point from Q=k*G (x1,y1)
-        //    $R = Gmp::doubleAndAdd($k_hex, $P);
-
-        //    $Rx_hex = Util::encodeHex($R->getX());
-        //    $Ry_hex = Util::encodeHex($R->getY());
-
-        //    while (strlen($Rx_hex) < 64) {
-        //        $Rx_hex = '0'.$Rx_hex;
-        //    }
-
-        //    while (strlen($Ry_hex) < 64) {
-        //        $Ry_hex = '0'.$Ry_hex;
-        //    }
-
-        //    // r = x1 mod n
-        //    $r = gmp_strval(gmp_mod('0x'.$Rx_hex, $n_hex));
-
-        //    // s = k^-1 * (e+d*r) mod n
-        //    $edr = gmp_add($e, gmp_mul($d, $r));
-        //    $invk = gmp_invert($k_hex, $n_hex);
-        //    $kedr = gmp_mul($invk, $edr);
-        //    $s = gmp_strval(gmp_mod($kedr, $n_hex));
-
-        //    // The signature is the pair (r,s)
-        //    $signature = array(
-        //        'r' => Util::encodeHex($r),
-        //        's' => Util::encodeHex($s),
-        //    );
-
-        //    while (strlen($signature['r']) < 64) {
-        //        $signature['r'] = '0'.$signature['r'];
-        //    }
-
-        //    while (strlen($signature['s']) < 64) {
-        //        $signature['s'] = '0'.$signature['s'];
-        //    }
-        //} while (gmp_cmp($r, '0') <= 0 || gmp_cmp($s, '0') <= 0);
-
-        //$sig = array(
-        //    'sig_rs' => $signature,
-        //    'sig_hex' => self::serializeSig($signature['r'], $signature['s']),
-        //);
-
-        //return $sig['sig_hex']['seq'];
     }
 
     /**
@@ -222,14 +147,12 @@ class Bitauth
     /**
      * Verifies a previously generated ECDSA signature
      *
-     * @param string
-     * @param string
      * @param array
      * @param array
      * @param string
      * @return boolean
      */
-    public function verifySignature($contract, $publicKey, $signature, $Q, $data)
+    public function verifySignature($signature, $Q, $data)
     {
         $Gx = '0x'.substr(Secp256k1::G, 0, 62);
         $Gy = '0x'.substr(Secp256k1::G, 64, 62);
@@ -262,20 +185,20 @@ class Bitauth
         // calculate u2 = r*w (mod n)
         $u2 = gmp_mod(gmp_mul($r, $w), $n_hex);
 
-        $P = array('x' => $Gx, 'y' => $Gy);
+        $P = new Point($Gx, $Gy);
 
         $Qx = '0x'.substr($Q, 2, 64);
         $Qy = '0x'.substr($Q, 66, 64);
 
-        $Q = array('x' => $Qx, 'y' => $Qy);
+        $Q = new Point($Qx, $Qy);
 
         // Get new point Z(x1,y1) = (u1 * G) + (u2 * Q)
-        $Za = Gmp::doubleAndAdd($u1, $P, $p_hex, $a_hex);
-        $Zb = Gmp::doubleAndAdd($u2, $Q, $p_hex, $a_hex);
-        $Z  = Gmp::gmpPointAdd($Za, $Zb, $p_hex, $a_hex);
+        $Za = Gmp::doubleAndAdd($u1, $P);
+        $Zb = Gmp::doubleAndAdd($u2, $Q);
+        $Z  = Gmp::gmpPointAdd($Za, $Zb);
 
-        $Zx_hex = Util::encodeHex($Z['x']);
-        $Zy_hex = Util::encodeHex($Z['y']);
+        $Zx_hex = Util::encodeHex($Z->getX());
+        $Zy_hex = Util::encodeHex($Z->getY());
 
         while (strlen($Zx_hex) < 64) {
             $Zx_hex = '0'.$Zx_hex;
diff --git a/src/Bitpay/PublicKey.php b/src/Bitpay/PublicKey.php
index fce40d3..e28800c 100644
--- a/src/Bitpay/PublicKey.php
+++ b/src/Bitpay/PublicKey.php
@@ -71,8 +71,12 @@ class PublicKey extends Key
      *
      * @return Bitpay\PublicKey
      */
-    public function generate()
+    public function generate(PrivateKey $privateKey = null)
     {
+        if ($privateKey instanceof PrivateKey) {
+            $this->setPrivateKey($privateKey);
+        }
+
         if (!empty($this->hex)) {
             return $this;
         }