diff --git a/src/Exception/TokenDecoderException.php b/src/Exception/TokenDecoderException.php
index 99c05be..87d8759 100644
--- a/src/Exception/TokenDecoderException.php
+++ b/src/Exception/TokenDecoderException.php
@@ -12,4 +12,24 @@ public function __construct(string $string, \Exception $e)
     {
         parent::__construct($string, self::CODE, $e);
     }
+
+    public static function forSignatureValidationFailure(\Exception $e): self
+    {
+        return new self('Signature validation failed', $e);
+    }
+
+    public static function forExpiration(\Exception $e): self
+    {
+        return new self('Token has expired', $e);
+    }
+
+    public static function forIssuerMismatch(\Exception $e): self
+    {
+        return new self('Issuer mismatch', $e);
+    }
+
+    public static function forAudienceMismatch(\Exception $e): self
+    {
+        return new self('Audience mismatch', $e);
+    }
 }
diff --git a/src/Interface/TokenDecoderInterface.php b/src/Interface/TokenDecoderInterface.php
index de18ae7..1463f8b 100644
--- a/src/Interface/TokenDecoderInterface.php
+++ b/src/Interface/TokenDecoderInterface.php
@@ -10,4 +10,10 @@ interface TokenDecoderInterface
      * @return array<string, mixed>
      */
     public function decode(string $token, string $key): array;
+
+    /**
+     * @param string $realm
+     * @param array<string, mixed> $tokenDecoded
+     */
+    public function validateToken(string $realm, array $tokenDecoded): void;
 }
diff --git a/src/Provider/KeycloakClient.php b/src/Provider/KeycloakClient.php
index 5ab5859..4d066ab 100644
--- a/src/Provider/KeycloakClient.php
+++ b/src/Provider/KeycloakClient.php
@@ -103,6 +103,7 @@ public function verifyToken(AccessTokenInterface $token): ?UserRepresentationDTO
 
             $decoder = TokenDecoderFactory::create($this->encryption_algorithm);
             $tokenDecoded = $decoder->decode($accessToken->getToken(), $this->encryption_key);
+            $decoder->validateToken($this->realm, $tokenDecoded);
             $this->keycloakClientLogger->info('KeycloakClient::verifyToken', [
                 'tokenDecoded' => $tokenDecoded,
             ]);
diff --git a/src/Token/HS256TokenDecoder.php b/src/Token/HS256TokenDecoder.php
index 93357f4..f1521d9 100644
--- a/src/Token/HS256TokenDecoder.php
+++ b/src/Token/HS256TokenDecoder.php
@@ -4,24 +4,41 @@
 
 namespace Mainick\KeycloakClientBundle\Token;
 
+use Firebase\JWT\JWT;
+use Firebase\JWT\Key;
 use Mainick\KeycloakClientBundle\Exception\TokenDecoderException;
 use Mainick\KeycloakClientBundle\Interface\TokenDecoderInterface;
 
 class HS256TokenDecoder implements TokenDecoderInterface
 {
+
     public function decode(string $token, string $key): array
     {
-        // https://github.com/firebase/php-jwt#example-encodedecode-headers
-        [$headersB64, $payloadB64, $sig] = explode('.', $token);
-        $tokenDecoded = json_decode(base64_decode($payloadB64), true, 512, JSON_THROW_ON_ERROR);
-
         try {
+            $tokenDecoded = JWT::decode($token, new Key($key, 'HS256'));
+
             $json = json_encode($tokenDecoded, JSON_THROW_ON_ERROR);
 
             return json_decode($json, true, 512, JSON_THROW_ON_ERROR);
-        }
-        catch (\Exception $e) {
+        } catch (\Exception $e) {
             throw new TokenDecoderException('Error decoding token', $e);
         }
     }
+
+    public function validateToken(string $realm, array $tokenDecoded): void
+    {
+        $now = time();
+
+        if ($tokenDecoded['exp'] < $now) {
+            throw TokenDecoderException::forExpiration(new \Exception('Token has expired'));
+        }
+
+        if (str_contains($tokenDecoded['iss'], $realm) === false) {
+            throw TokenDecoderException::forIssuerMismatch(new \Exception('Invalid token issuer'));
+        }
+//
+//        if ($tokenDecoded['aud'] !== 'account') {
+//            throw TokenDecoderException::forAudienceMismatch(new \Exception('Invalid token audience'));
+//        }
+    }
 }
diff --git a/src/Token/RS256TokenDecoder.php b/src/Token/RS256TokenDecoder.php
index 417b5fa..98dcdb0 100644
--- a/src/Token/RS256TokenDecoder.php
+++ b/src/Token/RS256TokenDecoder.php
@@ -13,17 +13,17 @@ class RS256TokenDecoder implements TokenDecoderInterface
 {
     public function decode(string $token, string $key): array
     {
-        $publicKeyPem = <<<EOD
+        try {
+            $publicKeyPem = <<<EOD
 -----BEGIN PUBLIC KEY-----
 $key
 -----END PUBLIC KEY-----
 EOD;
-        $publicKey = openssl_get_publickey($publicKeyPem);
+            $publicKey = openssl_get_publickey($publicKeyPem);
 
-        $headers = new \stdClass();
-        $tokenDecoded = JWT::decode($token, new Key($publicKey, 'RS256'), $headers);
+            $headers = new \stdClass();
+            $tokenDecoded = JWT::decode($token, new Key($publicKey, 'RS256'), $headers);
 
-        try {
             $json = json_encode($tokenDecoded, JSON_THROW_ON_ERROR);
 
             return json_decode($json, true, 512, JSON_THROW_ON_ERROR);
@@ -32,4 +32,13 @@ public function decode(string $token, string $key): array
             throw new TokenDecoderException('Error decoding token', $e);
         }
     }
+
+    public function validateToken(string $realm, array $tokenDecoded): void
+    {
+        $now = time();
+
+        if ($tokenDecoded['exp'] < $now) {
+            throw TokenDecoderException::forExpiration(new \Exception('Token has expired'));
+        }
+    }
 }
diff --git a/src/Token/TokenDecoderFactory.php b/src/Token/TokenDecoderFactory.php
index 0465118..08d9f8a 100644
--- a/src/Token/TokenDecoderFactory.php
+++ b/src/Token/TokenDecoderFactory.php
@@ -9,16 +9,16 @@
 
 class TokenDecoderFactory
 {
+    public const ALGORITHM_RS256 = 'RS256';
+    public const ALGORITHM_HS256 = 'HS256';
+
     #[Pure]
     public static function create($algorithm): TokenDecoderInterface
     {
-        switch ($algorithm) {
-            case 'RS256':
-                return new RS256TokenDecoder();
-            case 'HS256':
-                return new HS256TokenDecoder();
-            default:
-                throw new \RuntimeException('Invalid algorithm');
-        }
+        return match ($algorithm) {
+            self::ALGORITHM_RS256 => new RS256TokenDecoder(),
+            self::ALGORITHM_HS256 => new HS256TokenDecoder(),
+            default => throw new \RuntimeException('Invalid algorithm'),
+        };
     }
 }
diff --git a/tests/Provider/KeycloakClientTest.php b/tests/Provider/KeycloakClientTest.php
index 6f4fba2..ba05ef0 100644
--- a/tests/Provider/KeycloakClientTest.php
+++ b/tests/Provider/KeycloakClientTest.php
@@ -34,7 +34,7 @@ class KeycloakClientTest extends TestCase
   "exp": "%s",
   "iat": "%s",
   "jti": "e11a85c8-aa91-4f75-9088-57db4586f8b9",
-  "iss": "https://example.org/auth/realms/test-realm",
+  "iss": "https://example.org/auth/realms/mock_realm",
   "aud": "account",
   "nbf": "%s",
   "sub": "4332085e-b944-4acc-9eb1-27d8f5405f3e",
@@ -93,6 +93,8 @@ protected function setUp(): void
             'test-app',
             'mock_secret',
             'none',
+            self::ENCRYPTION_ALGORITHM,
+            self::ENCRYPTION_KEY
         );
 
         $jwt_tmp = sprintf($this->jwtTemplate, time() + 3600, time(), time());