Skip to content

Instantly share code, notes, and snippets.

@EvanMcBroom
Last active August 7, 2024 21:31
Show Gist options
  • Save EvanMcBroom/ad683e394f84b623da63c2b95f6fb547 to your computer and use it in GitHub Desktop.
Save EvanMcBroom/ad683e394f84b623da63c2b95f6fb547 to your computer and use it in GitHub Desktop.
Encrypt Strings at Compile Time
// Copyright (C) 2022 Evan McBroom
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// If you are using Visual Studio, you will need to disable the "Edit and Continue" feature.
// Prng based off of Parker Miller's
// "Multiplicative Linear Congruential Generator"
// https://en.wikipedia.org/wiki/Lehmer_random_number_generator
namespace mlcg {
constexpr uint32_t modulus() {
return 0x7fffffff;
}
// Create entropy using __FILE__ and __LINE__
template<size_t N>
constexpr uint32_t seed(const char(&entropy)[N], const uint32_t iv = 0) {
auto value{ iv };
for (size_t i{ 0 }; i < N; i++) {
// Xor 1st byte of seed with input byte
value = (value & ((~0) << 8)) | ((value & 0xFF) ^ entropy[i]);
// Rotl 1 byte
value = value << 8 | value >> ((sizeof(value) * 8) - 8);
}
// The seed is required to be less than the modulus and odd
while (value > modulus()) value = value >> 1;
return value << 1 | 1;
}
constexpr uint32_t prng(const uint32_t input) {
return (input * 48271) % modulus();
}
}
template<typename T, size_t N>
struct encrypted {
int seed;
T data[N];
};
template<size_t N>
constexpr auto crypt(const char(&input)[N], const uint32_t seed = 0) {
encrypted<char, N> blob{};
blob.seed = seed;
for (uint32_t index{ 0 }, stream{ seed }; index < N; index++) {
blob.data[index] = input[index] ^ stream;
stream = mlcg::prng(stream);
}
return blob;
}
#define make_string(STRING) ([&] { \
constexpr auto _{ crypt(STRING, mlcg::seed(__FILE__, __LINE__)) }; \
return std::string{ crypt(_.data, _.seed).data }; \
}())
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment