加密过程：
    E (Pi , Ki) = Pi (XOR) Ki
    解密：
    D (Ci , Ki) = Ci (XOR) Ki

    1. #include<bits/stdc++.h>
    2. using namespace std;
    3. int main()
    4. {
    5.     string plain, ciper, key;
    6.     int len; //长度三者一致
    7.     void change(string&, vector<int>&);//字符变数字
    8.     vector<int> encrypt_compute(vector<int> m, vector<int> k);//加密计算
    9.     vector<int> discrypt_compute(vector<int> c, vector<int> k);//解密计算
    10.     void re_change(vector<int>&, string&);//数字变字符
    12.     int flag; //操作标记
    13.     do
    14.     {
    15.         cout << "请选择操作：1、加密 2、解密 3、结束:";
    16.         cin >> flag;
    17.         if (flag == 1)
    18.         {
    19.             cout << "请输入明文:";
    20.             cin >> plain;
    21.             cout << "请输入相同长度的密钥:";
    22.             cin >> key;
    23.             len = plain.size();
    24.             vector<int> p, c, k; //存变换的数字
    25.             change(plain, p);
    26.             change(key, k); //字母->数字
    27.             c = encrypt_compute(p, k);
    28.             re_change(c, ciper); //数字->字母
    29.             cout << "密文是:" << ciper << endl;
    31.         }
    32.         if (flag == 2)
    33.         {
    34.             cout << "请输入密文:";
    35.             cin >> ciper;
    36.             cout << "请输入相同长度的密钥:";
    37.             cin >> key;
    38.             len = ciper.size();
    39.             vector<int> p, c, k; //存变换的数字
    40.             change(ciper, c);
    41.             change(key, k); //字母->数字
    42.             p = discrypt_compute(c, k);
    43.             plain = "";//清空明文原来的值
    44.             re_change(p, plain);
    45.             cout << "明文是:" << plain << endl;
    46.         }
    47.     } while (flag != 3);
    48.     return 0;
    49. }
    51. void change(string& plain, vector<int>& number) //字母变数字
    52. {
    53.     for (unsigned int i = 0; i < plain.size(); i++)
    54.     {
    55.         number.push_back(plain[i] - 97); //a为0
    56.     }
    57. }
    59. vector<int> encrypt_compute(vector<int> m, vector<int> k) //加密计算
    60. {
    61.     vector<int> sum;
    63.     for (unsigned int i = 0; i < m.size(); i++)
    64.     {
    65.         sum.push_back((m[i] + k[i]) % 26);
    66.     }
    67.     return sum;
    68. }
    70. vector<int> discrypt_compute(vector<int> c, vector<int> k) //解密计算
    71. {
    72.     vector<int> resum;
    73.     int temp;
    74.     for (unsigned int i = 0; i < c.size(); i++)
    75.     {
    76.         temp = c[i] - k[i];
    77.         if (temp < 0) temp += 26;
    78.         resum.push_back(temp);
    79.     }
    80.     return resum;
    82. }
    84. void re_change(vector<int>& sum, string& c) //数字变字符
    85. {
    86.     string temp;//用于处理insert函数变量传递
    87.     for (unsigned int i = 0; i < sum.size(); i++)
    88.     {
    89.         temp = sum[i] + 97;
    90.         c.insert(i, temp);//a为0
    91.     }
    93. }