Change MD5 Hash with Boost C++ Libraries & OpenSSL

std::string GetMD5Hash(const boost::filesystem::path& path)
{
    byte result[MD5_DIGEST_LENGTH];
    boost::iostreams::mapped_file_source source(path);
    MD5((byte*)source.data(), source.size(), result); // OpenSSL

    std::ostringstream s;
    s << std::hex << std::setfill('0');
    for (byte c : result)
        s << std::setw(2) << (int)c;
    return s.str();
}

bool ChangeMD5Hash(const boost::filesystem::path& path)
{
    boost::filesystem::path md5(path.string() + ".md5");
    if (boost::filesystem::exists(md5))
        boost::filesystem::remove(md5);
    if (boost::filesystem::exists(path))
        boost::filesystem::rename(path, md5);
    else
        return false;

    boost::random::mt19937 generator;
    boost::random::uniform_int_distribution<> random(1, 1024);

    boost::filesystem::ifstream istream(md5, std::ios::in | std::ios::binary);
    boost::filesystem::ofstream ostream(path, std::ios::out | std::ios::binary);
    if (!istream.is_open())
        return false;
    if (!ostream.is_open())
        return false;
    ostream << istream.rdbuf();
    ostream.seekp(istream.tellg());
    ostream.write("\0", random(generator));
    istream.close();
    ostream.close();
    return boost::filesystem::remove(md5);
}