@@ -554,14 +554,37 @@
      */
     static protected function bigNumToBin($bn)
     {
-        if (extension_loaded('gmp')) {
-        	$s = gmp_strval($bn, 16);
-        	if (strlen($s) % 2 != 0) {
-        		$s = '0' . $s;
-        	}
-            return pack("H*", $s);
-        } else if (extension_loaded('bcmath')) {
-            $cmp = bccomp($bn, 0);
+			if (extension_loaded('gmp')) {
+				$cmp = gmp_cmp($bn, 0);
+				if ($cmp < 0) {
+					throw new Zend_OpenId_Exception(
+						'Big integer arithmetic error',
+						Zend_OpenId_Exception::ERROR_LONG_MATH);
+				}
+				
+				if ($cmp == 0) {
+					return "\x00";
+				}
+				
+				$bytes = array();
+				
+				while (gmp_cmp($bn, 0) > 0) {
+					array_unshift($bytes, gmp_mod($bn, 256));
+					$bn = gmp_div($bn, pow(2, 8));
+				}
+				
+				if ($bytes && ($bytes[0] > 127)) {
+					array_unshift($bytes, 0);
+				}
+				
+				$string = '';
+				foreach ($bytes as $byte) {
+					$string .= pack('C', $byte);
+				}
+				
+				return $string;				
+			} else if (extension_loaded('bcmath')) {
+				$cmp = bccomp($bn, 0);
             if ($cmp == 0) {
                 return (chr(0));
             } else if ($cmp < 0) {