diff --git a/README.md b/README.md
index 1334879..351c20d 100644
--- a/README.md
+++ b/README.md
@@ -131,7 +131,7 @@ $TPV = new Redsys\Tpv\Tpv($config);
 # Realizamos la comprobación de la transacción
 
 try {
-    $datos = $TPV->checkTransaction($_POST);
+    $datos = $TPV->checkTransactionXml($_POST);
 } catch (Exception $e) {
     die(file_put_contents(__DIR__.'/logs/errores-tpv.log', $e->getMessage(), FILE_APPEND));
 }
diff --git a/src/Redsys/Tpv/Curl.php b/src/Redsys/Tpv/Curl.php
index f72aa11..827718b 100644
--- a/src/Redsys/Tpv/Curl.php
+++ b/src/Redsys/Tpv/Curl.php
@@ -1,7 +1,9 @@
 <?php
 namespace Redsys\Tpv;
 
-use DOMDocument, DOMXPath, Exception;
+use DOMDocument;
+use DOMXPath;
+use Exception;
 
 class Curl
 {
diff --git a/src/Redsys/Tpv/Debug.php b/src/Redsys/Tpv/Debug.php
index f0d8416..0ba1b09 100644
--- a/src/Redsys/Tpv/Debug.php
+++ b/src/Redsys/Tpv/Debug.php
@@ -19,7 +19,9 @@ public static function d($info, $title = '', $shift = 1)
         }
 
         echo '<code><strong>['.$last['line'].'] '.$row.'</strong></code>';
-        echo '<pre>'; var_dump($info); echo '</pre>';
+        echo '<pre>';
+        var_dump($info);
+        echo '</pre>';
     }
 
     public static function dd($info, $title = '')
diff --git a/src/Redsys/Tpv/Signature.php b/src/Redsys/Tpv/Signature.php
index 4814e97..0d3cbeb 100644
--- a/src/Redsys/Tpv/Signature.php
+++ b/src/Redsys/Tpv/Signature.php
@@ -5,21 +5,39 @@
 
 class Signature
 {
-    public static function fromValues($prefix, $values, $key)
+    public static function fromValues($prefix, array $values, $key)
     {
         $fields = array('Amount', 'Order', 'MerchantCode', 'Currency', 'TransactionType', 'MerchantURL');
 
         return self::calculate($prefix, $fields, $values, $key);
     }
 
-    public static function fromTransaction($prefix, $values, $key)
+    public static function fromTransaction($prefix, array $values, $key)
     {
         $fields = array('Amount', 'Order', 'MerchantCode', 'Currency', 'Response');
 
         return self::calculate($prefix, $fields, $values, $key);
     }
 
-    private static function calculate($prefix, $fields, $values, $key)
+    public static function fromTransactionXML($prefix, array $values, $key)
+    {
+        $fields = array('Amount', 'Order', 'MerchantCode', 'Currency', 'Response', 'TransactionType', 'SecurePayment');
+
+        return self::calculate($prefix, $fields, $values, $key);
+    }
+
+    public static function fromXML($xml, $key)
+    {
+        preg_match('#<DS_MERCHANT_ORDER>([^<]+)</DS_MERCHANT_ORDER>#i', $xml, $order);
+
+        if (empty($order[1])) {
+            throw new Exception('Can not be extracted Order from XML string');
+        }
+
+        return self::MAC256($xml, self::encryptKey($order[1], $key));
+    }
+
+    private static function calculate($prefix, array $fields, array $values, $key)
     {
         foreach ($fields as $field) {
             if (!isset($values[$prefix.$field])) {
@@ -27,9 +45,9 @@ private static function calculate($prefix, $fields, $values, $key)
             }
         }
 
-        $key = self::encrypt3DES($values[$prefix.'Order'], base64_decode($key));
+        $key = self::encryptKey($values[$prefix.'Order'], $key);
 
-        return base64_encode(hash_hmac('sha256', base64_encode(json_encode($values)), $key, true));
+        return self::MAC256(base64_encode(json_encode($values)), $key);
     }
 
     private static function encrypt3DES($message, $key)
@@ -38,4 +56,14 @@ private static function encrypt3DES($message, $key)
 
         return mcrypt_encrypt(MCRYPT_3DES, $key, $message, MCRYPT_MODE_CBC, $iv);
     }
-}
\ No newline at end of file
+
+    private static function encryptKey($order, $key)
+    {
+        return self::encrypt3DES($order, base64_decode($key));
+    }
+
+    private static function MAC256($string, $key)
+    {
+        return base64_encode(hash_hmac('sha256', $string, $key, true));
+    }
+}
diff --git a/src/Redsys/Tpv/Tpv.php b/src/Redsys/Tpv/Tpv.php
index 1cdfbc1..d0bd3ca 100644
--- a/src/Redsys/Tpv/Tpv.php
+++ b/src/Redsys/Tpv/Tpv.php
@@ -2,7 +2,8 @@
 namespace Redsys\Tpv;
 
 use Exception;
-use DOMDocument, DOMElement;
+use DOMDocument;
+use DOMElement;
 use Redsys\Messages\Messages;
 
 class Tpv
@@ -152,22 +153,17 @@ public function sendXml(array $options)
     {
         $this->values = array();
 
-        if (isset($options['Order'])) {
-            $options['Order'] = $this->getOrder($options['Order']);
-        }
-
-        if (isset($options['Amount'])) {
-            $options['Amount'] = $this->getAmount($options['Amount']);
-        }
+        $options['Order'] = $this->getOrder($options['Order']);
+        $options['Amount'] = $this->getAmount($options['Amount']);
 
         $this->setValueDefault($options, 'MerchantCode');
-        $this->setValueDefault($options, 'MerchantName');
-        $this->setValueDefault($options, 'MerchantData');
+        $this->setValueDefault($options, 'MerchantURL');
         $this->setValueDefault($options, 'Currency');
         $this->setValueDefault($options, 'Terminal');
-        $this->setValueDefault($options, 'TransactionType');
-        $this->setValueDefault($options, 'Order');
-        $this->setValueDefault($options, 'Amount');
+
+        $this->setValue($options, 'TransactionType');
+        $this->setValue($options, 'Order');
+        $this->setValue($options, 'Amount');
 
         $Curl = new Curl(array(
             'base' => $this->getPath('')
@@ -175,7 +171,9 @@ public function sendXml(array $options)
 
         $Curl->setHeader(CURLOPT_HTTPHEADER, array('Content-Type: application/x-www-form-urlencoded'));
 
-        return $Curl->post('/operaciones', array(), 'entrada='.$this->xmlArray2string($this->setXmlValues()));
+        return $Curl->post('/operaciones', array(
+            'entrada' => $this->xmlArray2string($this->setXmlValues())
+        ));
     }
 
     private function setXmlValues()
@@ -192,19 +190,18 @@ private function setXmlValues()
     private function xmlArray2string($xml)
     {
         $doc = new DOMDocument();
-        $doc->formatOutput = true;
 
         $data = $doc->createElement('DATOSENTRADA');
 
         foreach ($xml as $key => $value) {
-            $data->appendChild((new DOMElement($key, $value)));
+            $data->appendChild((new DOMElement(strtoupper($key), $value)));
         }
 
         $root = $doc->createElement('REQUEST');
 
-        $root->appendChild(new DOMElement('DS_SIGNATUREVERSION', $this->options['SignatureVersion']));
-        $root->appendChild(new DOMElement('DS_SIGNATURE', $this->getValuesSignature()));
         $root->appendChild($data);
+        $root->appendChild(new DOMElement('DS_SIGNATUREVERSION', $this->options['SignatureVersion']));
+        $root->appendChild(new DOMElement('DS_SIGNATURE', Signature::fromXML((string)$doc->saveXML($data), $this->options['Key'])));
 
         $doc->appendChild($root);
 
@@ -216,6 +213,31 @@ public function xmlString2array($xml)
         return json_decode(json_encode(simplexml_load_string($xml)), true);
     }
 
+    public function checkTransactionXml(array $post)
+    {
+        $prefix = 'Ds_';
+
+        if (empty($post) || empty($post[$prefix.'Signature']) || empty($post[$prefix.'MerchantParameters'])) {
+            throw new Exception('_POST data is empty');
+        }
+
+        $data = $this->getTransactionParameters($post);
+        $data = $this->xmlString2array($data['datos']);
+
+        if (empty($data)) {
+            throw new Exception('_POST data can not be decoded');
+        }
+
+        $this->checkTransactionError($data, $prefix);
+        $this->checkTransactionResponse($data, $prefix);
+
+        $signature = Signature::fromTransactionXml($prefix, $data, $this->options['Key']);
+
+        $this->checkTransactionSignature($signature, $post[$prefix.'Signature']);
+
+        return array_merge($post, $data);
+    }
+
     private function setValueDefault(array $options, $option)
     {
         $code = $this->option_prefix.$option;
@@ -291,16 +313,33 @@ public function checkTransaction(array $post)
             throw new Exception('_POST data can not be decoded');
         }
 
+        $this->checkTransactionError($data, $prefix);
+        $this->checkTransactionResponse($data, $prefix);
+
+        $signature = Signature::fromTransaction($prefix, $data, $this->options['Key']);
+
+        $this->checkTransactionSignature($signature, $post[$prefix.'Signature']);
+
+        return array_merge($post, array_map('urldecode', $data));
+    }
+
+    private function checkTransactionError(array $data, $prefix)
+    {
         $error = isset($data[$prefix.'ErrorCode']) ? $data[$prefix.'ErrorCode'] : null;
 
-        if ($error) {
-            if ($message = Messages::getByCode($error)) {
-                throw new Exception(sprintf('TPV returned error code %s: %s', $error, $message['message']));
-            } else {
-                throw new Exception(sprintf('TPV returned unknown error code %s', $error));
-            }
+        if (empty($error)) {
+            return null;
         }
 
+        if ($message = Messages::getByCode($error)) {
+            throw new Exception(sprintf('TPV returned error code %s: %s', $error, $message['message']));
+        } else {
+            throw new Exception(sprintf('TPV returned unknown error code %s', $error));
+        }
+    }
+
+    private function checkTransactionResponse(array $data, $prefix)
+    {
         $response = isset($data[$prefix.'Response']) ? $data[$prefix.'Response'] : null;
 
         if (is_null($response) || (strlen($response) === 0)) {
@@ -314,19 +353,18 @@ public function checkTransaction(array $post)
                 throw new Exception(sprintf('Response code is unknown %s', $response));
             }
         }
+    }
 
-        $signature = Signature::fromTransaction($prefix, $data, $this->options['Key']);
-
-        $postSignature = strtr($post[$prefix.'Signature'], '-_', '+/');
+    private function checkTransactionSignature($signature, $postSignature)
+    {
+        $postSignature = strtr($postSignature, '-_', '+/');
 
         if ($signature !== $postSignature) {
             throw new Exception(sprintf('Signature not valid (%s != %s)', $signature, $postSignature));
         }
-
-        return array_merge($post, array_map('urldecode', $data));
     }
 
-    private function getTransactionParameters(array $post)
+    public function getTransactionParameters(array $post)
     {
         return json_decode(base64_decode(strtr($post['Ds_MerchantParameters'], '-_', '+/')), true);
     }
diff --git a/src/autoload.php b/src/autoload.php
index ad5b819..afc95ef 100644
--- a/src/autoload.php
+++ b/src/autoload.php
@@ -1,6 +1,5 @@
 <?php
-spl_autoload_register(function ($className)
-{
+spl_autoload_register(function ($className) {
     if (strpos($className, 'Redsys\\Tpv') !== 0) {
         return;
     }