diff --git a/cp/app/Controllers/Auth/AuthController.php b/cp/app/Controllers/Auth/AuthController.php
index 3a3b214..24f5747 100644
--- a/cp/app/Controllers/Auth/AuthController.php
+++ b/cp/app/Controllers/Auth/AuthController.php
@@ -112,12 +112,11 @@ class AuthController extends Controller
         
         try {
             $db = $container->get('db');
-            $user = $db->selectValue('SELECT id FROM users WHERE email = ?', [$data['email']]);
+            $userId = $db->selectValue('SELECT id FROM users WHERE email = ?', [$data['email']]);
 
-            if ($user) {
+            if ($userId) {
                 // User found, get the user ID
-                $userId = $user;
-                $registrations = $db->select('SELECT id,credential_id FROM users_webauthn WHERE user_id = ?', [$user]);
+                $registrations = $db->select('SELECT id,credential_id FROM users_webauthn WHERE user_id = ?', [$userId]);
             
                 if ($registrations) {
                     foreach ($registrations as $reg) {
@@ -141,8 +140,7 @@ class AuthController extends Controller
         $getArgs = $this->webAuthn->getGetArgs($ids, 60*4, true, true, true, true, true, 'required');
 
         $response->getBody()->write(json_encode($getArgs));
-        $challenge = $this->webAuthn->getChallenge();
-        $_SESSION['challenge_data'] = $challenge->getBinaryString();
+        $_SESSION['challenge'] = $this->webAuthn->getChallenge();
 
         return $response->withHeader('Content-Type', 'application/json');
     }
@@ -151,8 +149,7 @@ class AuthController extends Controller
     {
         global $container;
         
-        $challengeData = $_SESSION['challenge_data'];
-        $challenge = new \lbuchs\WebAuthn\Binary\ByteBuffer($challengeData);
+        $challenge = $_SESSION['challenge'];
         $credentialPublicKey = null;
         
         $data = json_decode($request->getBody()->getContents(), null, 512, JSON_THROW_ON_ERROR);
@@ -185,7 +182,7 @@ class AuthController extends Controller
             }
 
             // process the get request. throws WebAuthnException if it fails
-            $this->webAuthn->processGet($clientDataJSON, $authenticatorData, $signature, $credentialPublicKey, $challengeData, null, 'required');       
+            $this->webAuthn->processGet($clientDataJSON, $authenticatorData, $signature, $credentialPublicKey, $challenge, null, 'required');       
 
             $return = new \stdClass();
             $return->success = true;
diff --git a/cp/app/Controllers/ProfileController.php b/cp/app/Controllers/ProfileController.php
index 7b7522b..6c414d9 100644
--- a/cp/app/Controllers/ProfileController.php
+++ b/cp/app/Controllers/ProfileController.php
@@ -148,17 +148,13 @@ class ProfileController extends Controller
         $createArgs = $this->webAuthn->getCreateArgs(\hex2bin($hexUserId), $userEmail, $userName, 60*4, null, 'required', null);
 
         $response->getBody()->write(json_encode($createArgs));
-        $challenge = $this->webAuthn->getChallenge();
-        $_SESSION['challenge_data'] = $challenge->getBinaryString();
-
+        $_SESSION['challenge'] = $this->webAuthn->getChallenge();
+        
         return $response->withHeader('Content-Type', 'application/json');
     }
     
     public function verifyRegistration(Request $request, Response $response)
     {
-        $challengeData = $_SESSION['challenge_data'];
-        //$challenge = new \lbuchs\WebAuthn\Binary\ByteBuffer($challengeData);
-
         global $container;
         $data = json_decode($request->getBody()->getContents(), null, 512, JSON_THROW_ON_ERROR);
         $userName = $_SESSION['auth_username'];
@@ -171,10 +167,10 @@ class ProfileController extends Controller
             $attestationObject = base64_decode($data->attestationObject);
 
             // Retrieve the challenge from the session
-            //$challenge = $_SESSION['challenge'];
+            $challenge = $_SESSION['challenge'];
 
             // Process the WebAuthn response
-            $credential = $this->webAuthn->processCreate($clientDataJSON, $attestationObject, $challengeData, 'required', true, false);
+            $credential = $this->webAuthn->processCreate($clientDataJSON, $attestationObject, $challenge, 'required', true, false);
             
             // add user infos
             $credential->userId = $userId;