function PBKDF2_Broken($p, $s, $c, $kl)
 {
     $hl = strlen(sha256('test')) / 2;
     $kb = ($kl + ($hl - $kl % $hl)) / $hl;
     $dk = '';
     for ($bn = 1; $bn <= $kb; $bn++) {
         $ib = $b = WPOnlineBackup_Functions::hash_hmac_sha256_Broken($s . pack('N', $bn), $p, true);
         for ($i = 1; $i < $c; $i++) {
             $ib ^= $b = WPOnlineBackup_Functions::hash_hmac_sha256_Broken($b, $p, true);
         }
         $dk .= $ib;
     }
     return substr($dk, 0, $kl);
 }