1. #include <bits/stdc++.h>
    2. using namespace std;
    4. typedef struct{
    5.     int row;
    6.     int col;
    7. }position;          //矩阵中位置
    9. char KeyMat[5][5];  // 密钥矩阵
    11. //由密钥生成矩阵
    12. void generateMatrix(string key)
    13. {
    14.     int flag[26] = {0};    //记录是否重复
    15.     int x = 0, y = 0;
    17.     //将key值填入矩阵
    18.     for(int i=0; i<key.length(); i++)
    19.     {
    20.         if(key[i] == 'j') key[i] = 'i';  // 用 i 代替 j
    22.         if(flag[key[i]-'a'] == 0)        //只有未出现的字母,flag=0
    23.         {
    24.             KeyMat[x][y++] = key[i];     //写入矩阵
    25.             flag[key[i]-'a'] = 1;        //记录该字母已出现
    26.         }
    27.         if(y==5) x++, y=0;               //每行五个字母
    28.     }
    30.     //填剩余字母
    31.     for(char ch = 'a'; ch <= 'z'; ch++)
    32.     {
    33.         if(ch == 'j') continue;  //跳过j
    35.         if(flag[ch - 'a'] == 0)
    36.         {
    37.             KeyMat[x][y++] = ch;
    38.             flag[ch - 'a'] = 1 ;
    39.         }
    40.         if(y==5) x++, y=0;
    41.     }
    42. }
    44. //填充不相关字母 x
    45. string formatMessage(string msg)
    46. {
    48.     for (int i = 0; i < msg.length(); i++)     //将j换为i
    49.     {
    50.         if (msg[i] == 'j')  msg[i] = 'i';
    51.     }
    52.     for(int ii=1; ii<msg.length(); ii+=2) //比较
    53.     {
    54.         if (msg[ii - 1] == msg[ii])  msg.insert(ii, "x");   //若相邻元素相同,填充x
    56.     }
    57.     if(msg.length()%2 != 0)  msg += "x";                   //若明文总数为奇数,填充x
    58.     return msg;
    59. }
    61. //返回字符再矩阵中的位置
    62. position getPosition(char c)
    63. {
    64.     for(int i=0; i<5; i++)
    65.         for(int j=0; j<5; j++)
    66.             if(c == KeyMat[i][j])
    67.             {
    68.                 position p = {i, j};
    69.                 return p;
    70.             }
    71. }
    73. //加密
    74. string encrypt(string message)
    75. {
    76.     string ctext = "";
    77.     for(int i=0; i<message.length(); i+=2)    // i+2,成对加密
    78.     {
    79.         position p1 = getPosition(message[i]);
    80.         position p2 = getPosition(message[i+1]);
    81.         int x1 = p1.row; int y1 = p1.col;
    82.         int x2 = p2.row; int y2 = p2.col;
    84.         if( x1 == x2 )       //同行:右移
    85.         {
    86.             ctext +=  KeyMat[x1][(y1+1)%5];
    87.             ctext +=  KeyMat[x2][(y2+1)%5];
    88.         }
    89.         else if( y1 == y2 )  // 同列:下移
    90.         {
    91.             ctext += KeyMat[ (x1+1)%5 ][ y1 ];
    92.             ctext += KeyMat[ (x2+1)%5 ][ y2 ];
    93.         }
    94.         else                 //不同行同列,取交叉元素
    95.         {
    96.             ctext += KeyMat[ x1 ][ y2 ];
    97.             ctext += KeyMat[ x2 ][ y1 ];
    98.         }
    99.     }
    100.     return ctext;
    101. }
    103. //解密
    104. string Decrypt(string message)
    105. {
    106.     string ptext = "";
    107.     for(int i=0; i<message.length(); i+=2) // 成对解密
    108.     {
    109.         position p1 = getPosition(message[i]);
    110.         position p2 = getPosition(message[i+1]);
    111.         int x1 = p1.row; int y1 = p1.col;
    112.         int x2 = p2.row; int y2 = p2.col;
    114.         if( x1 == x2 )       // 同行:左移
    115.         {
    116.             ptext += KeyMat[x1][ --y1<0 ? 4: y1 ];
    117.             ptext += KeyMat[x2][ --y2<0 ? 4: y2 ];
    118.         }
    119.         else if( y1 == y2 )   // 同列:上移
    120.         {
    121.             ptext += KeyMat[ --x1<0 ? 4: x1 ][y1];
    122.             ptext += KeyMat[ --x2<0 ? 4: x2 ][y2];
    123.         }
    124.         else
    125.         {
    126.             ptext += KeyMat[ x1 ][ y2 ];
    127.             ptext += KeyMat[ x2 ][ y1 ];
    128.         }
    129.     }
    130.     return ptext;
    131. }
    133. int main()
    134. {    
    135.     string x;
    136.     string plaintext;
    137.     cout << "输入明文 : "; 
    138.     cin >> plaintext;   //储存明文
    140.     string key="qazwsxedcrfvtgbyhnujmikolp";        //密钥
    142.     for (int i = 0; i < key.length(); i++)
    143.     {
    144.         generateMatrix(key);   //生成密钥矩阵
    145.     }
    147.     cout << "密钥矩阵: " << endl;
    148.     for (int k = 0; k < 5; k++)
    149.     {
    150.         for (int j = 0; j < 5; j++)
    151.         {
    152.             cout << KeyMat[k][j] << "  ";
    153.         }
    154.         cout << endl;
    155.     }
    157.     cout << "明文: \t\t: " << plaintext << endl;
    159.     string fmsg = formatMessage(plaintext);
    160.     cout << "填充后的明文 \t: " << fmsg << endl;
    162.     string ciphertext = encrypt(fmsg);
    163.     cout << "加密后的密文: \t: " << ciphertext << endl;
    165.     string decryptmsg = Decrypt(ciphertext);
    166.     cout<< "解密后为: \t: " << decryptmsg << endl;
    168. }