function randHash($length) {
    $hash = '';
    if ($length>2) {
      $alphabet = str_split('qwertyuiopasdfghjklzxcvbnm');
      for($i = 0; $i < 2; $i++) {
          $hash .= $alphabet[array_rand($alphabet)];
      }
      $length-=2;
    }
    $alphabet = str_split('qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890');
    for($i = 0; $i < $length; $i++) {
        $hash .= $alphabet[array_rand($alphabet)];
    }
    return $hash;
}

$key = md5($_POST['address'] . ' ' . randHash(rand(10, 12)));

$_SESSION["key"] = $key;

$claim_url .= '&key=' . rawurlencode($key);