C语言实现维吉尼亚密码的示例代码
#include
#include
#define MAXSIZE 100
#define KEY 50
int Encryption(char* Plaintext, char* key) //加密算法
{
int i = 0, j = strlen(key), k = strlen(Plaintext),m=0;
char result[MAXSIZE] = {0};
for (i = 0; i < k; i++)
{
if (Plaintext[i] != ' '&& Plaintext[i] >= 'a' && Plaintext[i] <= 'z')//明文是小写字母
{
if (key[m % j] >= 'a' && key[m % j] <= 'z')//密钥为小写字母
{
result[i] = (Plaintext[i] + key[m % j] - 2 * 'a') % 26 + 'a';
}
else if (key[m % j] >= 'A' && key[m % j] <= 'Z')//密钥为大写字母
{
result[i] = (Plaintext[i] + key[m % j] - 'A'-'a') % 26 + 'a';
}
m++;
}
else if (Plaintext[i] != ' ' && Plaintext[i] >= 'A' && Plaintext[i] <= 'Z')//明文是大写字母
{
if (key[m % j] >= 'a' && key[m % j] <= 'z')//密钥为小写字母
{
result[i] = (Plaintext[i] + key[m % j] - 'a' - 'A') % 26 + 'A';
}
else if (key[m % j] >= 'A' && key[m % j] <= 'Z')//密钥为大写字母
{
result[i] = (Plaintext[i] + key[m % j] - 'A' - 'A') % 26 + 'A';
}
m++;
}
else
result[i] = ' ';
}
printf("加密后的密文为：%s
",result);
return 0;
}
int Decrypt(char* Ciphertext, char* key)//解密算法
{
int i = 0, j = strlen(key), k = strlen(Ciphertext),m=0;
char result[MAXSIZE] = { 0 };
for (i = 0; i < k; i++)
{
if (Ciphertext[i] != ' ' && Ciphertext[i] >= 'a' && Ciphertext[i] <= 'z')//明文是小写字母
{
if (key[m % j] >= 'a' && key[m % j] <= 'z')//密钥为小写字母
{
result[i] = (Ciphertext[i] + 26 - (key[m % j] - 'a') - 'a') % 26 + 'a';
}
else if (key[m % j] >= 'A' && key[m % j] <= 'Z')//密钥为大写字母
{
result[i] = (Ciphertext[i] + 26 - (key[m % j] - 'A') - 'a') % 26 + 'a';
}
m++;
}
else if (Ciphertext[i] != ' ' && Ciphertext[i] >= 'A' && Ciphertext[i] <= 'Z')//明文是大写字母
{
if (key[m % j] >= 'a' && key[m % j] <= 'z')//密钥为小写字母
{
result[i] = (Ciphertext[i] + 26 - (key[m % j] - 'a') - 'A') % 26 + 'A';
}
else if (key[m % j] >= 'A' && key[m % j] <= 'Z')//密钥为大写字母
{
result[i] = (Ciphertext[i] + 26 - (key[m % j] - 'A') - 'A') % 26 + 'A';
}
m++;
}
else
result[i] = ' ';
}
printf("解密后的明文为：%s
", result);
return 0;
}
int main()
{
int n;
char Plaintext[MAXSIZE] = {0};
char Ciphertext[MAXSIZE] = {0};
char key[KEY] = {0};
while (1)
{
printf("===============
");
printf(" 1.加密
");
printf(" 2.解密
");
printf(" 0.退出
");
printf("===============
");
printf("请输入要执行的操作：");
scanf_s("%d",&n);
getchar();
switch (n)
{
case 1:
printf("请输入明文：");
scanf_s("%[^
]", Plaintext, MAXSIZE);
getchar();
printf("请输入密钥：");
scanf_s("%[^
]", key, KEY);
Encryption(Plaintext, key);
break;
case 2:
printf("请输入密文：");
scanf_s("%[^
]", Ciphertext, MAXSIZE);
getchar();
printf("请输入密钥：");
scanf_s("%[^
]", key, KEY);
Decrypt(Ciphertext, key);
break;
case 0:
exit(0);
break;
}
}
return 0;
}