diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 95aa009f..fbe85724 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -21,6 +21,7 @@
       recepción de pagos, page 22* it is required that  `pagos10:Pago@Monto` must be in an interval.
     - Fix samples from `tests/assets/pagos/` since new validation make it fail.
     - Rename validation class `MontoGreaterOrEqualThanSumOfDocuments` to `MontoBetweenIntervalSumOfDocuments`
+- Refactor `CfdiUtils\Certificado\Certificado` extracting obtain public key routine to an internal method.
 - Create tests for trait `CalculateDocumentAmountTrait`.
 
 
diff --git a/src/CfdiUtils/Certificado/Certificado.php b/src/CfdiUtils/Certificado/Certificado.php
index cb2103a1..a1e3f4c1 100644
--- a/src/CfdiUtils/Certificado/Certificado.php
+++ b/src/CfdiUtils/Certificado/Certificado.php
@@ -53,21 +53,7 @@ public function __construct(string $filename)
         }
 
         // get the public key
-        $pubkey = false;
-        $pubData = false;
-        try {
-            $pubkey = openssl_get_publickey($contents);
-            if (is_resource($pubkey)) {
-                $pubData = openssl_pkey_get_details($pubkey);
-            }
-        } finally {
-            if (is_resource($pubkey)) {
-                openssl_free_key($pubkey);
-            }
-        }
-        if (false === $pubData) {
-            $pubData = ['key' => ''];
-        }
+        $pubKey = $this->obtainPubKeyFromContents($contents);
 
         // set all the values
         $this->rfc = (string) strstr($data['subject']['x500UniqueIdentifier'] . ' ', ' ', true);
@@ -84,7 +70,7 @@ public function __construct(string $filename)
         $this->serial = $serial->asAscii();
         $this->validFrom = $data['validFrom_time_t'];
         $this->validTo = $data['validTo_time_t'];
-        $this->pubkey = $pubData['key'];
+        $this->pubkey = $pubKey;
         $this->pemContents = $contents;
         $this->filename = $filename;
     }
@@ -206,4 +192,24 @@ protected function changeCerToPem(string $contents): string
             . chunk_split(base64_encode($contents), 64, PHP_EOL)
             . '-----END CERTIFICATE-----' . PHP_EOL;
     }
+
+    protected function obtainPubKeyFromContents(string $contents): string
+    {
+        try {
+            $pubkey = openssl_get_publickey($contents);
+            if (! is_resource($pubkey)) {
+                return '';
+            }
+            $pubData = openssl_pkey_get_details($pubkey);
+            if (false === $pubData) {
+                return '';
+            }
+            return $pubData['key'] ?? '';
+        } finally {
+            // close public key even if the flow is throw an exception
+            if (isset($pubkey) && is_resource($pubkey)) {
+                openssl_free_key($pubkey);
+            }
+        }
+    }
 }