protected function normalizeParts(array $parts)
    {
        $blockSize = $this->getPartSize();
        $callback  = function ($value) {
            return Util::safeStrlen($value);
        };
        $maxSize = max(array_map($callback, $parts));
        if ($maxSize % $blockSize != 0) {
            $maxSize += $blockSize - ($maxSize % $blockSize);
        }
        foreach ($parts as &$part) {
            $part = $this->str_pad($part, $maxSize, chr(0));
            $part = str_split($part, $blockSize);
        }

        return $parts;
    }