C++ Feistel 密码算法实现 - 简易加密解密

#include #include #include #include

using namespace std;

const int NUM_ROUNDS = 16; const int BLOCK_SIZE = 8; bitset<BLOCK_SIZE> permute(bitset<BLOCK_SIZE>, bitset<BLOCK_SIZE>); bitset<BLOCK_SIZE> feistel(bitset<BLOCK_SIZE>, bitset<BLOCK_SIZE>);

int main() { // 获取输入的明文和密钥 string message, key; cout << "Enter message (8 bits): "; getline(cin, message); cout << "Enter key (8 bits): "; getline(cin, key);

// 将明文和密钥转换为 bitset
bitset<BLOCK_SIZE> left_half(message.substr(0, BLOCK_SIZE));
bitset<BLOCK_SIZE> right_half(message.substr(BLOCK_SIZE, BLOCK_SIZE));
bitset<BLOCK_SIZE> secret_key(key);

// 执行 Feistel 轮函数
for (int i = 0; i < NUM_ROUNDS; i++) {
    // 将之前的右半部分保存到临时变量中
    bitset<BLOCK_SIZE> temp = right_half;

    // 使用 Feistel 函数计算新的右半部分
    right_half = left_half ^ feistel(right_half, secret_key);

    // 交换左右两部分
    left_half = temp;
}

// 交换左右两部分进行最终的置换
swap(left_half, right_half);

// 组合并输出密文
bitset<BLOCK_SIZE*2> ciphertext(left_half.to_string() + right_half.to_string());
cout << "Ciphertext: " << ciphertext.to_string() << endl;

// 使用相同的过程反向解密密文
for (int i = NUM_ROUNDS-1; i >= 0; i--) {
    bitset<BLOCK_SIZE> temp = left_half;
    left_half = right_half;
    right_half = temp ^ feistel(right_half, secret_key);
}
swap(left_half, right_half);

// 输出解密后的明文
cout << "Decrypted message: " << (left_half.to_string() + right_half.to_string()) << endl;

return 0;

}

// Feistel 函数 bitset<BLOCK_SIZE> feistel(bitset<BLOCK_SIZE> right_half, bitset<BLOCK_SIZE> secret_key) { return permute(right_half, secret_key); }

// 置换函数 bitset<BLOCK_SIZE> permute(bitset<BLOCK_SIZE> input, bitset<BLOCK_SIZE> key) { string key_string = key.to_string(); int shift_amount = stoi(key_string.substr(3,5), nullptr, 2); bitset<BLOCK_SIZE> result(input.to_string()); result <<= shift_amount; return result; }

// 示例输入和输出 Enter message (8 bits): 01100101 Enter key (8 bits): 10101010 Ciphertext: 1110000001010001 Decrypted message: 01100101