四种加密解密算法的源代码：移位密码、仿射密码、维吉尼亚密码以及置换密码

四种加密解密算法的源代码：移位密码、仿射密码、维吉尼亚密码以及置换密码

#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <malloc.h>
void Shift() /*移位密码*/
{
char c[100];
int length, i=0, key=0;
clrscr();

printf("********Shift Cipher********/nPlease input primal sentence: ");
gets(c);
length = strlen(c);
printf("Input the key(0~26): ");
scanf("%d", &key);
getchar();

if(key<0)
{
printf("The value of key is error!/nPress any key to return...");
getch();
return;
}
for(i=0; i<length; i++)
{
if(c[i]>96&&c[i]<123)
c[i] = (c[i]+key-97)%26+65;
else if(c[i]>64&&c[i]<91)
c[i] = (c[i]+key-65)%26+65;
}
printf("Result is: %s/n", c);
for(i=0; i<length; i++)
{
if(c[i]>64&&c[i]<91)
c[i] = (c[i]-key-65+26)%26+97;
}
printf("/nAfter translated the sentence,we can see the primal sentence as follow:/n%s/n", c);
printf("Press any key to return...");
getch();
}

int gcd(int a, int b) /*辗转相除法求a,b的最大公因数*/
{
int k = 0;

do
{
k = a%b;
a = b;
b = k;
}while(k!=0);
return a;
}

int Ni(int a, int b) /*求a相对于b的逆*/
{
int i = 0;
while(a*(++i)%b!=1);
return i;
}

void Affine() /*仿射密码*/
{
char c[100];
int length, i=0, ka=0, kb=0, tmp;
clrscr();

printf("********Affine Cipher********/nPlease input primal sentence: ");
gets(c);
length = strlen(c);
printf("Input the key(2 numbers): ");
scanf("%d%d", &ka, &kb);
getchar();
if(gcd(ka,26)!=1)
{
printf("The value of the key is error!/nPress any key to return...");
return;
}

for(i=0; i<length; i++)
{
if(c[i]>96&&c[i]<123)
c[i] = (ka*(c[i]-97)+kb)%26+65;
else if(c[i]>64&&c[i]<91)
c[i] = (ka*(c[i]-65)+kb)%26+65;
}
printf("Result is: %s/n", c);
for(i=0; i<length; i++)
{
if(c[i]>64&&c[i]<91)
{
tmp = Ni(ka,26)*((c[i]-65)-kb);
if(tmp<0)
c[i] = tmp%26+26+97;
else
c[i] = tmp%26+97;
}
}
printf("/nAfter translated the sentence,we can see the primal sentence as follow:/n%s/n", c);
printf("Press any key to return...");
getch();
}

void Vigenere() /*维吉利亚密码*/
{
char c[100], key[100];
int lenc, lenk, i=0, j=0, tmp;
clrscr();

printf("********Vigenere Cipher********/nPlease input primal sentence: ");
gets(c);
lenc = strlen(c);
strcpy(c, strupr(c));
printf("Input the key: ");
gets(key);
lenk = strlen(key);
strcpy(key, strupr(key));
for(; i<lenc; i++)
{
j = j%lenk;
if(c[i]>64&&c[i]<91)
{
c[i] = (c[i]-65+key[j]-65)%26+65;
j++;
}
}
printf("Result is: %s/n", c);
for(i=0, j=0; i<lenc; i++)
{
j = j%lenk;
if(c[i]>64&&c[i]<91)
{
tmp = c[i]-65-(key[j]-65);
if(tmp>=0)
c[i] = tmp%26+97;
else
c[i] = (tmp+26)%26+97;
j++;
}
}
printf("/nAfter translated the sentence,we can see the primal sentence as follow:/n%s/n", c);
printf("Press any key to return...");
getch();
}

void Permutation() /*置换密码*/
{
char c[100], *q;
int *key, len, m, i, j=0;
clrscr();

printf("********Permutation Cipher********/nPlease input primal sentence: ");
gets(c);
strcpy(c, strupr(c));
len = strlen(c);
for(i=0; i<len; i++)
{
if(c[i]<65||c[i]>90)
{
for(j=i; j<len-1; j++)
c[j] = c[j+1];
len--;
}
}
c[len] = '/0';
printf("Input the length of the key: ");
scanf("%d", &m);
key = (int)malloc(m*sizeof(int));
q = (int)malloc(len*sizeof(int));
printf("Input the key: ");
for(i=0; i<m; i++)
{
scanf("%d", key+i);
key[i]--;
}
getchar();

for(i=0; i<len; i++)
{
j = (i/m)*m;
q[i] = c[*(key+i%m)+j];
}
q[i] = '/0';

printf("Result is: %s/n", q);

for(i=0, j=0; i<len; i++)
{
j = (i/m)*m;
c[*(key+i%m)+j] = q[i]+32;
}
c[len] = '/0';

printf("After translated the sentence,we can see the primal sentence as follow:/n%s/n", c);
printf("Press any key to return...");
free(key);
free(q);
getch();
}

void main()
{
char i = '0';
clrscr();

while(i!='5')
{
clrscr();
printf("********Press 1~5 to choose:********/n");
printf("1. Shift Cipher/n2. Affine Cipher/n3. Vigenere Cipher/n4. Permutation Cipher/n5. Exit/n");
i = getch();
if(i=='1')
Shift();
else if(i=='2')
Affine();
else if(i=='3')
Vigenere();
else if(i=='4')
Permutation();
else if(i=='5')
break;
}
}