118 lines
2.7 KiB
C++
118 lines
2.7 KiB
C++
#include <iostream>
|
|
#include <sstream>
|
|
#include <array>
|
|
|
|
#define BLOCK_SIZE 8
|
|
#define N_ROUNDS 8
|
|
|
|
std::string F(std::string m, const std::string& key);
|
|
std::string Xor(const std::string& a, const std::string& b);
|
|
std::string Shiftl(const std::string& s, std::size_t amount);
|
|
std::string Shiftr(const std::string& s, std::size_t amount);
|
|
std::pair<std::string, std::string> Feistel(std::string l, std::string r, const std::array<std::string, 8>& keys, bool reverseKeyOrder = false);
|
|
|
|
int Mod(int numerator, int denominator)
|
|
{
|
|
return (denominator + (numerator % denominator)) % denominator;
|
|
}
|
|
|
|
int main()
|
|
{
|
|
std::string l = "10101010";
|
|
std::string r = "10101010";
|
|
const std::array<std::string, 8> keys = {
|
|
"11101101",
|
|
"01110101",
|
|
"10111101",
|
|
"00010110",
|
|
"00000011",
|
|
"10110011",
|
|
"11011101",
|
|
"00111101"
|
|
};
|
|
|
|
std::cout << "Input: " << l << r << std::endl;
|
|
|
|
auto c = Feistel(l, r, keys);
|
|
l = c.first;
|
|
r = c.second;
|
|
|
|
std::cout << "Ciphertext: " << l << r << std::endl;
|
|
|
|
c = Feistel(l, r, keys, true);
|
|
l = c.first;
|
|
r = c.second;
|
|
|
|
std::cout << "Decrypted: " << l << r << std::endl;
|
|
|
|
return 0;
|
|
}
|
|
|
|
std::pair<std::string, std::string> Feistel(std::string l, std::string r, const std::array<std::string, 8>& keys, bool reverseKeyOrder)
|
|
{
|
|
std::string tmp;
|
|
|
|
for (std::size_t i = 0; i < N_ROUNDS; i++)
|
|
{
|
|
// Calculate key index
|
|
std::size_t keyIndex;
|
|
if (reverseKeyOrder)
|
|
keyIndex = N_ROUNDS - i - 1;
|
|
else
|
|
keyIndex = i;
|
|
|
|
// Do a feistel round
|
|
tmp = r;
|
|
r = Xor(l, F(r, keys[keyIndex]));
|
|
l = tmp;
|
|
}
|
|
|
|
return std::make_pair(r, l);
|
|
}
|
|
|
|
std::string F(std::string m, const std::string& key)
|
|
{
|
|
// Made-up F function
|
|
|
|
// Shift 5 to the left
|
|
m = Shiftl(m, 5);
|
|
|
|
// Xor with key
|
|
return Xor(m, key);
|
|
}
|
|
|
|
std::string Shiftl(const std::string& s, std::size_t amount)
|
|
{
|
|
std::stringstream ss;
|
|
|
|
for (std::size_t i = 0; i < s.size(); i++)
|
|
ss << s[Mod((i + amount), s.size())];
|
|
|
|
return ss.str();
|
|
}
|
|
|
|
std::string Shiftr(const std::string& s, std::size_t amount)
|
|
{
|
|
std::stringstream ss;
|
|
|
|
for (std::size_t i = 0; i < s.size(); i++)
|
|
ss << s[Mod((i - amount), s.size())];
|
|
|
|
return ss.str();
|
|
}
|
|
|
|
std::string Xor(const std::string& a, const std::string& b)
|
|
{
|
|
std::stringstream ss;
|
|
|
|
for (std::size_t i = 0; i < BLOCK_SIZE; i++)
|
|
{
|
|
if (a[i] xor b[i])
|
|
ss << '1';
|
|
else
|
|
ss << '0';
|
|
}
|
|
|
|
return ss.str();
|
|
}
|