Index: typo3/sysext/openid/lib/php-openid/Auth/OpenID/HMAC.php
===================================================================
--- typo3/sysext/openid/lib/php-openid/Auth/OpenID/HMAC.php	(revision 17369)
+++ typo3/sysext/openid/lib/php-openid/Auth/OpenID/HMAC.php	(working copy)
@@ -56,7 +56,12 @@
  */
 function Auth_OpenID_HMACSHA1($key, $text)
 {
-    if (Auth_OpenID::bytes($key) > Auth_OpenID_SHA1_BLOCKSIZE) {
+	if (function_exists('hash_hmac') && function_exists('hash_algos') && in_array('sha1', hash_algos())) {
+		return hash_hmac('sha1', $text, $key, true);
+	}
+
+	// Home-made solution
+	if (Auth_OpenID::bytes($key) > Auth_OpenID_SHA1_BLOCKSIZE) {
         $key = Auth_OpenID_SHA1($key, true);
     }