dcfb7075-dda0-3838-1240-fa218c561313.cpp

#include <bits/stdc++.h>
using namespace std;

/*
class lfsr():
    def __init__(self, seed, mask, length):
        self.length_mask = 2 ** length - 1
        self.mask = mask & self.length_mask
        self.state = seed & self.length_mask
        print(self.state, self.mask)

    def next(self):
        next_state = (self.state << 1) & self.length_mask
        output = count_one(self.state & self.mask & self.length_mask)
        next_state ^= output  # 最低位为 0，相当于 |
        self.state = next_state
        return output

    def getrandbit(self, nbit):
        output = 0
        for _ in range(nbit):
            output = (output << 1) ^ self.next()
        return output
*/

void decrypt(const uint32_t &mask)
{
    vector<uint32_t> codes = {205,
                              197,
                              241,
                              3,
                              18,
                              128,
                              36,
                              253,
                              5,
                              200,
                              170,
                              131,
                              25,
                              71,
                              9,
                              196,
                              164,
                              161,
                              9,
                              0,
                              7,
                              123,
                              149,
                              121,
                              32,
                              122,
                              149,
                              131,
                              170,
                              252,
                              189,
                              68,
                              162,
                              164,
                              153,
                              67};
    uint32_t state = (249u << 24) | (16u << 16) | (69u << 8) | (218u);
    for (const auto &code : codes)
    {
        // cout << code;
        uint32_t num = 0u;
        for (int j = 0; j < 8; ++j)
        {
            uint32_t next_state = state << 1, output = popcount(state & mask) & 1;
            next_state ^= output;
            state = next_state;
            num <<= 1;
            num ^= output;
        }
        auto c = code ^ num;
        if (isalnum(c) || c == '{' || c == '}')
        {
            // cout << c << endl;
            cout << (char)(c);
        }
    }
    cout << endl;
}

int main()
{
    uint32_t array[3] = {153u, 131u, 138u};
    for (uint32_t mask = 0; mask < numeric_limits<uint32_t>::max(); ++mask)
    {
        uint32_t state = (249u << 24) | (16u << 16) | (69u << 8) | (218u);
        bool flag = true;
        uint32_t num;

        for (int i = 0; i < 3 && flag; ++i)
        {
            num = 0u;
            for (int j = 0; j < 8; ++j)
            {
                uint32_t next_state = state << 1, output = popcount(state & mask) & 1;
                next_state ^= output;
                state = next_state;
                num <<= 1;
                num ^= output;
            }
            if (num != array[i])
            {
                flag = false;
            }
        }
        if (flag)
        {
            for (int i = 3; i < 36; ++i)
            {
                num = 0u;
                for (int j = 0; j < 8; ++j)
                {
                    uint32_t next_state = state << 1, output = popcount(state & mask) & 1;
                    next_state ^= output;
                    state = next_state;
                    num <<= 1;
                    num ^= output;
                }
            }
            if (num == 62u)
            {
                cout << mask << endl;
            }
        }
    }

    vector<uint32_t> masks = {2226048585};
    for (const auto &mask : masks)
    {
        decrypt(mask);
    }
}