from: http://dxlib.o.oo7.jp/cgi/patiobbs/patio.cgi?mode=view&no=4371

inferior_encrypted_string.hpp

/*=============================================================================
  Copyright (C) 2018 yumetodo <yume-wikijp@live.jp>
  Distributed under the Boost Software License, Version 1.0.
  (See https://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
//ref: http://dxlib.o.oo7.jp/cgi/patiobbs/patio.cgi?mode=view&no=4371
#include <string>

#if defined(__clang__)
#   if !__has_feature(cxx_constexpr)
#	  define DXLIB_CUSTOM_NO_CXX11_CONSTEXPR
#   endif
#   if !__has_feature(cxx_noexcept)
#	    define DXLIB_CUSTOM_NO_CXX11_NOEXCEPT
#   endif
#   if !__has_feature(cxx_relaxed_constexpr)
#	  define DXLIB_CUSTOM_NO_CXX14_CONSTEXPR
#   endif
#elif defined(__GNUC__)
#   if defined(__GXX_EXPERIMENTAL_CXX0X__) || (__cplusplus >= 201103L)
#       define DXLIB_CUSTOM_GCC_CXX11
#   endif
#   if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 6) || !defined(DXLIB_CUSTOM_GCC_CXX11))
#	    define DXLIB_CUSTOM_NO_CXX11_CONSTEXPR
#	    define DXLIB_CUSTOM_NO_CXX11_NOEXCEPT
#   endif
#   if !defined(__cpp_constexpr) || (__cpp_constexpr < 201304)
#	    define DXLIB_CUSTOM_NO_CXX14_CONSTEXPR
#   endif
#elif defined(_MSC_VER)
#   if _MSC_FULL_VER < 190023026
#	    define DXLIB_CUSTOM_NO_CXX11_CONSTEXPR
#       define DXLIB_CUSTOM_NO_CXX11_NOEXCEPT
#   endif
#   if !defined(__cpp_constexpr) || (__cpp_constexpr < 201304)
#	  define DXLIB_CUSTOM_NO_CXX14_CONSTEXPR
#   endif
#endif

#ifdef DXLIB_CUSTOM_NO_CXX11_CONSTEXPR
#   define DXLIB_CUSTOM_CONSTEXPR
#else
#   define DXLIB_CUSTOM_CONSTEXPR constexpr
#   include <type_traits>
#endif

#ifdef DXLIB_CUSTOM_NO_CXX11_NOEXCEPT
#   define DXLIB_CUSTOM_NOEXCEPT
#else
#   define DXLIB_CUSTOM_NOEXCEPT noexcept
#endif

namespace inferior_encrypted_string {
    template<typename CharType, std::size_t N>
    struct inferior_encrypted_string {
        CharType str[N];
        //typedef std::basic_string<CharType> string_t;
        std::basic_string<CharType> decrypt() const
        {
            std::basic_string<CharType> re = this->str;
            for(typename std::basic_string<CharType>::iterator it = re.begin(); it != re.end(); ++it) *it += CharType(31);
            return re;
        }
    };
#if !defined(DXLIB_CUSTOM_NO_CXX11_CONSTEXPR) && defined(DXLIB_CUSTOM_NO_CXX14_CONSTEXPR)
    template <class T>
    constexpr T&& forward(typename std::remove_reference<T>::type& t) noexcept { return static_cast<T&&>(t); }
    template <class T>
    constexpr T&& forward(typename std::remove_reference<T>::type&& t) noexcept { return static_cast<T&&>(t); }
    namespace detail {

        template<typename CharType, std::size_t N, std::size_t i, typename std::enable_if<(0 == i), std::nullptr_t>::type, typename ...RestChars>
        constexpr inferior_encrypted_string<CharType, N>make_inferior_encrypted_string_impl(const CharType (& str)[N], RestChars&& ...rest) noexcept
        {
            return {{ CharType(str[0] - 31), forward<CharType>(rest)... }};
        }
        template<typename CharType, std::size_t N, std::size_t i, typename std::enable_if<(0 != i), std::nullptr_t>::type, typename ...RestChars>
        constexpr inferior_encrypted_string<CharType, N> make_inferior_encrypted_string_impl(const CharType (& str)[N], RestChars&& ...rest) noexcept
        {
            return make_inferior_encrypted_string_impl<CharType, N, i - 1, nullptr, RestChars...>(str, CharType(str[i] - 31), forward<CharType>(rest)...);
        }
    }
    template<typename CharType, std::size_t N>
    constexpr inferior_encrypted_string<CharType, N> make_inferior_encrypted_string(const CharType (& str)[N]) noexcept
    {
        return detail::make_inferior_encrypted_string_impl<CharType, N, N - 2, nullptr>(str, CharType('\0'));
    }
#else
    template<typename CharType, std::size_t N>
    DXLIB_CUSTOM_CONSTEXPR inferior_encrypted_string<CharType, N> make_inferior_encrypted_string(const CharType (& str)[N]) DXLIB_CUSTOM_NOEXCEPT
    {
#   if defined(DXLIB_CUSTOM_NO_CXX11_CONSTEXPR) && defined(DXLIB_CUSTOM_NO_CXX14_CONSTEXPR)
        inferior_encrypted_string<CharType, N> re;
#   else
        //In constexpr function, uninitialized variable is not parmitted
        inferior_encrypted_string<CharType, N> re{};
#   endif
        for(std::size_t i = 0; i < N - 1; ++i) re.str[i] = CharType(str[i] - 31);
        re.str[N - 1] = CharType('\0');
        return re;
    }
#endif
}

main.cpp

#include "inferior_encrypted_string.hpp"
#include <iostream>
#if defined(DXLIB_CUSTOM_NO_CXX11_CONSTEXPR) && defined(DXLIB_CUSTOM_NO_CXX14_CONSTEXPR)
const inferior_encrypted_string::inferior_encrypted_string<char, sizeof("arikitari")> s1 = inferior_encrypted_string::make_inferior_encrypted_string("arikitari");
const inferior_encrypted_string::inferior_encrypted_string<char, sizeof("ありきたりな世界")> s2 = inferior_encrypted_string::make_inferior_encrypted_string("ありきたりな世界");
#else
constexpr auto s1 = inferior_encrypted_string::make_inferior_encrypted_string("arikitari");
constexpr auto s2 = inferior_encrypted_string::make_inferior_encrypted_string("ありきたりな世界");
#endif
int main()
{
    std::cout
        << s1.str << std::endl
        << s1.decrypt() << std::endl
        << std::endl
        << s2.str << std::endl
        << s2.decrypt() << std::endl;
}

動作例: https://wandbox.org/permlink/SOsUuAvhLRbFeWUS

C++03でもコンパイルが通るようにだけした。ただし簡易暗号化機能はない。暗号化は実行時に行われる

https://wandbox.org/permlink/dZcxjgQkyzma7gNi