用希尔密码进行加密解密

要求:1.加密矩阵最好是随机的或者一种明文对应一种；
2.不得将对角矩阵作为加密矩阵；
3.有思路解析和步骤说明
4.执行框内需要显示明文、加密矩阵、解密矩阵、密文

程序输出：

Enter 3x3 matrix for key (should have inverse):
1
0
1
2
4
0
3
5
6

Enter a string of 3 letter(use A through Z): ABC

Encrypted string is: CER

Inverse Matrix is:
1.09091 0.227273 -0.181818
-0.545455 0.136364 0.0909091
-0.0909091 -0.227273 0.181818

Decrypted string is: ABC

--------------------------------
Process exited after 37.64 seconds with return value 0
请按任意键继续. . .

源程序：

#include<iostream>
#include<math.h>
using namespace std;
float en[3][1], de[3][1], a[3][3], b[3][3], msg[3][1], m[3][3];
void getKeyMatrix() { //get key and message from user
   int i, j;
   char mes[3];
   cout<<"Enter 3x3 matrix for key (should have inverse):\n";
   for(i = 0; i < 3; i++)
   for(j = 0; j < 3; j++) {
      cin>>a[i][j];
      m[i][j] = a[i][j];
   }
   cout<<"\nEnter a string of 3 letter(use A through Z): ";
   cin>>mes;
   for(i = 0; i < 3; i++)
   msg[i][0] = mes[i] - 65;
}
void encrypt() { //encrypts the message
   int i, j, k;
   for(i = 0; i < 3; i++)
   for(j = 0; j < 1; j++)
   for(k = 0; k < 3; k++)
   en[i][j] = en[i][j] + a[i][k] * msg[k][j];
   cout<<"\nEncrypted string is: ";
   for(i = 0; i < 3; i++)
   cout<<(char)(fmod(en[i][0], 26) + 65); //modulo 26 is taken for each element of the matrix obtained by multiplication
}
void inversematrix() { //find inverse of key matrix
   int i, j, k;
   float p, q;
   for(i = 0; i < 3; i++)
   for(j = 0; j < 3; j++) {
      if(i == j)
         b[i][j]=1;
      else
         b[i][j]=0;
   }
   for(k = 0; k < 3; k++) {
      for(i = 0; i < 3; i++) {
         p = m[i][k];
         q = m[k][k];
         for(j = 0; j < 3; j++) {
            if(i != k) {
               m[i][j] = m[i][j]*q - p*m[k][j];
               b[i][j] = b[i][j]*q - p*b[k][j];
            }
         }
      }
   }
   for(i = 0; i < 3; i++)
   for(j = 0; j < 3; j++)
   b[i][j] = b[i][j] / m[i][i];
   cout<<"\n\nInverse Matrix is:\n";
   for(i = 0; i < 3; i++) {
      for(j = 0; j < 3; j++)
      cout<<b[i][j]<<" ";
      cout<<"\n";
   }
}
void decrypt() { //decrypt the message
   int i, j, k;
   inversematrix();
   for(i = 0; i < 3; i++)
   for(j = 0; j < 1; j++)
   for(k = 0; k < 3; k++)
   de[i][j] = de[i][j] + b[i][k] * en[k][j];
   cout<<"\nDecrypted string is: ";
   for(i = 0; i < 3; i++)
   cout<<(char)(fmod(de[i][0], 26) + 65); //modulo 26 is taken to get the original message
   cout<<"\n";
}
int main() {
   getKeyMatrix();
   encrypt();
   decrypt();
}

文档参考地址：
https://zditect.com/main-advanced/cpp/cplusplus-program-to-implement-the-hill-cyphe.html

提供参考实例，期望对你有所帮助：https://www.cnblogs.com/SuperBird/p/Mrszdblog.html

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