在编译时创建哈希值和/或加密字符串？
在编译时创建哈希值和/或加密字符串？
提问于 2018-06-19 03:15:47
有没有办法在编译时为字符串或加密字符串创建散列值？我希望将生成加密文本或散列值的原始字符串直接放入代码中作为字符串文字，但我不希望它们以未转换的形式编译成可执行文件。
像这样的东西？
constexpr uint32 hash(const char * string){
... // turns a string into a value to represent it
}
constexpr std::string encrypt(const char * string){
... // turns a string into a cyphertext (unsure what return type would work best here)
}
void f(){
std::string input << std::cin();
switch(hashedKey){
case hash("help"): // legal?
if(0 == encryptRT(input).compare(encrypt("secret string")){
// the secret string should never appear in the executable
}
break;
}
}非常重要的一点是，不要将直接放入常量表达式函数中的字符串放入字符串表中。这个是可能的吗？
回答 1
Stack Overflow用户
发布于 2018-06-19 03:38:09
编译时xor混淆的示例：
#include <iostream>
#include <iomanip>
#include <cstddef>
#include <cstdint>
#include <array>
template<::std::size_t x_data_bytes_count, ::std::size_t x_key_bytes_count> constexpr auto
obfuscate
(
::std::array<::std::uint8_t, x_data_bytes_count> const & input
, ::std::array<::std::uint8_t, x_key_bytes_count> const & key
) noexcept
{
static_assert(::std::size_t{0} < x_data_bytes_count);
// Assuming null-terminated string is used as a key.
static_assert(::std::size_t{1} < x_key_bytes_count);
::std::array<::std::uint8_t, x_data_bytes_count> output{};
::std::size_t data_byte_index{};
::std::size_t key_byte_index{};
do
{
output[data_byte_index] = input[data_byte_index] xor key[key_byte_index];
data_byte_index = data_byte_index + ::std::size_t{1};
key_byte_index = key_byte_index + ::std::size_t{1};
key_byte_index = key_byte_index % (key.size() - ::std::size_t{1});
}
while(input.size() != data_byte_index);
return output;
}
// Following two overloads may accept string literals
// so calling obfuscation function would be more convenient.
template<::std::size_t x_data_bytes_count, ::std::size_t x_key_bytes_count> constexpr auto
obfuscate
(
char const ( & input )[x_data_bytes_count]
, char const ( & key )[x_key_bytes_count]
) noexcept
{
::std::size_t byte_index{};
::std::array<::std::uint8_t, x_data_bytes_count> input_arr{};
for(byte_index = 0; x_data_bytes_count != byte_index; ++byte_index)
{
input_arr[byte_index] = static_cast<::std::uint8_t>(input[byte_index]);
}
::std::array<::std::uint8_t, x_key_bytes_count> key_arr{};
for(byte_index = 0; x_key_bytes_count != byte_index; ++byte_index)
{
key_arr[byte_index] = static_cast<::std::uint8_t>(key[byte_index]);
}
return obfuscate(input_arr, key_arr);
}
template<::std::size_t x_data_bytes_count, ::std::size_t x_key_bytes_count> constexpr auto
obfuscate
(
::std::array<::std::uint8_t, x_data_bytes_count> const & input_arr
, char const ( & key )[x_key_bytes_count]
) noexcept
{
::std::size_t byte_index{};
::std::array<::std::uint8_t, x_key_bytes_count> key_arr{};
for(byte_index = 0; x_key_bytes_count != byte_index; ++byte_index)
{
key_arr[byte_index] = static_cast<::std::uint8_t>(key[byte_index]);
}
return obfuscate(input_arr, key_arr);
}
int main()
{
constexpr auto const & key{"Stack overflow"};
constexpr auto const obfuscated_str{obfuscate("Hello World!", key)};
for(auto const & ch: obfuscated_str)
{
::std::cout << ::std::hex << ::std::setw(2) << ::std::setfill('0')
<< static_cast<::std::uint32_t>(ch) << " ";
}
::std::cout << ::std::endl;
auto const deobfuscated_str{obfuscate(obfuscated_str, key)};
for(auto const & ch: deobfuscated_str)
{
::std::cout << ::std::hex << ::std::setw(2) << ::std::setfill('0')
<< static_cast<::std::uint32_t>(ch) << " ";
}
::std::cout << ::std::endl;
::std::cout << reinterpret_cast<char const *>(deobfuscated_str.data()) << ::std::endl;
return 0;
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/50916099
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