diff --git a/.cs.php b/.cs.php
index 2bba5e9..a113324 100644
--- a/.cs.php
+++ b/.cs.php
@@ -19,7 +19,7 @@
             'array_syntax' => ['syntax' => 'short'],
             'cast_spaces' => ['space' => 'none'],
             'concat_space' => ['spacing' => 'one'],
-            'compact_nullable_typehint' => true,
+            'compact_nullable_type_declaration' => true,
             'declare_equal_normalize' => ['space' => 'single'],
             'general_phpdoc_annotation_remove' => [
                 'annotations' => [
diff --git a/src/Algorithm.php b/src/Algorithm.php
index 54151c8..f8a3058 100644
--- a/src/Algorithm.php
+++ b/src/Algorithm.php
@@ -56,7 +56,7 @@ final class Algorithm
      * @param string $signatureMethodAlgorithm
      * @param string|null $digestMethodAlgorithm
      */
-    public function __construct(string $signatureMethodAlgorithm, string $digestMethodAlgorithm = null)
+    public function __construct(string $signatureMethodAlgorithm, ?string $digestMethodAlgorithm = null)
     {
         $this->setSignatureMethodAlgorithm($signatureMethodAlgorithm);
         $this->setDigestMethodAlgorithm($digestMethodAlgorithm ?? $signatureMethodAlgorithm);
diff --git a/src/X509Reader.php b/src/X509Reader.php
index 125b4e7..a9b1c67 100644
--- a/src/X509Reader.php
+++ b/src/X509Reader.php
@@ -74,6 +74,6 @@ public function toRawBase64(OpenSSLCertificate $certificate): string
 
         preg_match(self::PEM_REGEX_PATTERN, $exportedCertificate, $matches);
 
-        return str_replace(["\r\n", "\n"], '', trim($matches[1]));
+        return str_replace(["\r\n", "\n"], '', trim($matches[1] ?? ''));
     }
 }
diff --git a/src/XmlSignatureVerifier.php b/src/XmlSignatureVerifier.php
index d9ea208..af43fe6 100644
--- a/src/XmlSignatureVerifier.php
+++ b/src/XmlSignatureVerifier.php
@@ -19,16 +19,23 @@ final class XmlSignatureVerifier
 
     private bool $preserveWhiteSpace;
 
+    private bool $exclusive;
+
     /**
      * The constructor.
      *
      * @param CryptoVerifierInterface $cryptoVerifier
      * @param bool $preserveWhiteSpace To remove redundant white spaces
+     * @param bool $exclusive Exclusive canonicalization. @see https://www.php.net/manual/en/domnode.c14n.php
      */
-    public function __construct(CryptoVerifierInterface $cryptoVerifier, bool $preserveWhiteSpace = true)
-    {
+    public function __construct(
+        CryptoVerifierInterface $cryptoVerifier, 
+        bool $preserveWhiteSpace = true, 
+        bool $exclusive = true,
+    ) {
         $this->cryptoVerifier = $cryptoVerifier;
         $this->preserveWhiteSpace = $preserveWhiteSpace;
+        $this->exclusive = $exclusive;
         $this->xmlReader = new XmlReader();
     }
 
@@ -82,13 +89,13 @@ public function verifyDocument(DOMDocument $xml): bool
             $signatureValueElement = $this->xmlReader->queryDomNode($xpath, '//xmlns:SignatureValue', $signedInfoNode);
             $signatureValueElement->nodeValue = '';
 
-            $canonicalData = $signedInfoNode->C14N(true, false);
+            $canonicalData = $signedInfoNode->C14N($this->exclusive, false);
 
             $xml2 = new DOMDocument();
             $xml2->preserveWhiteSpace = true;
             $xml2->formatOutput = true;
             $xml2->loadXML($canonicalData);
-            $canonicalData = $xml2->C14N(true, false);
+            $canonicalData = $xml2->C14N($this->exclusive, false);
 
             $isValidSignature = $this->cryptoVerifier->verify($canonicalData, $signatureValue, $signatureAlgorithm);
 
@@ -124,8 +131,8 @@ private function checkDigest(DOMDocument $xml, DOMXPath $xpath, string $algorith
             $signatureNode->parentNode->removeChild($signatureNode);
         }
 
-        // Canonicalize the content, exclusive and without comments
-        $canonicalData = $xml->C14N(true, false);
+        // Canonicalize the content without comments
+        $canonicalData = $xml->C14N($this->exclusive, false);
 
         $digestValue2 = $this->cryptoVerifier->computeDigest($canonicalData, $algorithm);
 
diff --git a/src/XmlSigner.php b/src/XmlSigner.php
index 1b28466..21da694 100644
--- a/src/XmlSigner.php
+++ b/src/XmlSigner.php
@@ -20,9 +20,18 @@ final class XmlSigner
 
     private CryptoSignerInterface $cryptoSigner;
 
-    public function __construct(CryptoSignerInterface $cryptoSigner)
-    {
+    private bool $preserveWhiteSpace;
+
+    private bool $exclusive;
+
+    public function __construct(
+        CryptoSignerInterface $cryptoSigner, 
+        bool $preserveWhiteSpace = true, 
+        bool $exclusive = true,
+    ) {
         $this->xmlReader = new XmlReader();
+        $this->preserveWhiteSpace = $preserveWhiteSpace;
+        $this->exclusive = $exclusive;
         $this->cryptoSigner = $cryptoSigner;
     }
 
@@ -42,7 +51,7 @@ public function signXml(string $data): string
         $xml = new DOMDocument();
 
         // Whitespaces must be preserved
-        $xml->preserveWhiteSpace = true;
+        $xml->preserveWhiteSpace = $this->preserveWhiteSpace;
         $xml->formatOutput = false;
 
         $xml->loadXML($data);
@@ -63,7 +72,7 @@ public function signXml(string $data): string
      *
      * @return string The signed XML as string
      */
-    public function signDocument(DOMDocument $document, DOMElement $element = null): string
+    public function signDocument(DOMDocument $document, ?DOMElement $element = null): string
     {
         $element = $element ?? $document->documentElement;
 
@@ -71,7 +80,7 @@ public function signDocument(DOMDocument $document, DOMElement $element = null):
             throw new XmlSignerException('Invalid XML document element');
         }
 
-        $canonicalData = $element->C14N(true, false);
+        $canonicalData = $element->C14N($this->exclusive, false);
 
         // Calculate and encode digest value
         $digestValue = $this->cryptoSigner->computeDigest($canonicalData);
@@ -176,11 +185,11 @@ private function appendSignature(DOMDocument $xml, string $digestValue): void
         }
 
         // http://www.soapclient.com/XMLCanon.html
-        $c14nSignedInfo = $signedInfoElement->C14N(true, false);
+        $c14nSignedInfo = $signedInfoElement->C14N($this->exclusive, false);
 
         $signatureValue = $this->cryptoSigner->computeSignature($c14nSignedInfo);
 
-        $xpath = new DOMXpath($xml);
+        $xpath = new DOMXPath($xml);
         $signatureValueElement = $this->xmlReader->queryDomNode($xpath, '//SignatureValue', $signatureElement);
         $signatureValueElement->nodeValue = base64_encode($signatureValue);
     }
diff --git a/tests/XmlSignatureTest.php b/tests/XmlSignatureTest.php
index 53d6246..f237f31 100644
--- a/tests/XmlSignatureTest.php
+++ b/tests/XmlSignatureTest.php
@@ -48,38 +48,43 @@ public function testSignAndVerify(string $privateKeyFile, string $publicKeyFile,
 
         foreach ($files as $filename) {
             foreach ($algos as $algo) {
-                $privateKeyStore = new PrivateKeyStore();
+                $this->testFileAndAlgo($filename, $algo, $privateKeyFile, $publicKeyFile, $password);
+            }
+        }
+    }
 
-                if (pathinfo($privateKeyFile, PATHINFO_EXTENSION) === 'p12') {
-                    $privateKeyStore->loadFromPkcs12(file_get_contents($privateKeyFile), $password);
-                } else {
-                    $privateKeyStore->loadFromPem(file_get_contents($privateKeyFile), $password);
-                }
+    private function testFileAndAlgo(string $filename, string $algo, string $privateKeyFile, string $publicKeyFile, string $password)
+    {
+        $privateKeyStore = new PrivateKeyStore();
 
-                $algorithm = new Algorithm($algo, $algo);
-                $cryptoSigner = new CryptoSigner($privateKeyStore, $algorithm);
+        if (pathinfo($privateKeyFile, PATHINFO_EXTENSION) === 'p12') {
+            $privateKeyStore->loadFromPkcs12(file_get_contents($privateKeyFile), $password);
+        } else {
+            $privateKeyStore->loadFromPem(file_get_contents($privateKeyFile), $password);
+        }
 
-                $xmlSigner = new XmlSigner($cryptoSigner);
-                $xmlSigner->setReferenceUri('');
+        $algorithm = new Algorithm($algo, $algo);
+        $cryptoSigner = new CryptoSigner($privateKeyStore, $algorithm);
 
-                $signedXml = $xmlSigner->signXml(file_get_contents($filename));
+        $xmlSigner = new XmlSigner($cryptoSigner);
+        $xmlSigner->setReferenceUri('');
 
-                // verify
-                $publicKeyStore = new PublicKeyStore();
-                if (pathinfo($publicKeyFile, PATHINFO_EXTENSION) === 'p12') {
-                    $publicKeyStore->loadFromPkcs12(file_get_contents($publicKeyFile), $password);
-                } else {
-                    $publicKeyStore->loadFromPem(file_get_contents($publicKeyFile));
-                }
+        $signedXml = $xmlSigner->signXml(file_get_contents($filename));
 
-                $cryptoVerifier = new CryptoVerifier($publicKeyStore);
-                $xmlSignatureVerifier = new XmlSignatureVerifier($cryptoVerifier);
+        // verify
+        $publicKeyStore = new PublicKeyStore();
+        if (pathinfo($publicKeyFile, PATHINFO_EXTENSION) === 'p12') {
+            $publicKeyStore->loadFromPkcs12(file_get_contents($publicKeyFile), $password);
+        } else {
+            $publicKeyStore->loadFromPem(file_get_contents($publicKeyFile));
+        }
 
-                $isValid = $xmlSignatureVerifier->verifyXml($signedXml);
+        $cryptoVerifier = new CryptoVerifier($publicKeyStore);
+        $xmlSignatureVerifier = new XmlSignatureVerifier($cryptoVerifier);
 
-                $this->assertTrue($isValid);
-            }
-        }
+        $isValid = $xmlSignatureVerifier->verifyXml($signedXml);
+
+        $this->assertTrue($isValid);
     }
 
     /**