Vigenere Cipher Implementation > C Program

Vigenere Cipher Implementation > C Program

Cryptography and System Security

Program:

#include<stdio.h>

void main()

{

int i;

int kl;

int pl;

printf("Enter the length of the key stream. ");

scanf("%d",&kl);

printf("Enter the length of the plain text stream.(Without spaces) ");

scanf("%d",&pl);

char p[pl];

char k[kl];

printf("\nEnter the Key. ");

for(i=-1;i<kl;++i)

scanf("%c",&k[i]);

printf("\nEnter the Plain text. ");

for(i=-1;i<pl;++i)

scanf("%c",&p[i]);

int s[3][pl];

for(i=0;i<pl;++i)

{

if(65<=p[i] && p[i]<=91)

s[0][i]=p[i]%65;

else

s[0][i]=p[i]%97;

}

for(i=0;i<pl;++i)

printf("%d ",s[0][i]);

int count=0;

while(count<pl)

{

for(i=0;i<kl;++i)

{

if(65<=k[i] && k[i]<=91)

s[1][count+i]=k[i]%65;

else

s[1][count+i]=k[i]%97;

}

count=count+kl;

}

printf("\n");

for(i=0;i<pl;++i)

printf("%d ",s[1][i]);

printf("\n");

for(i=0;i<pl;++i)

printf("%d ",s[2][i]);

printf("\n\nThe cipher text is: ");

char cipher[kl];

for(i=0;i<pl;++i)

{

s[2][i]=(s[0][i]+s[1][i])%26;

cipher[i]=(char)(s[2][i]+65);

printf("%c ",cipher[i]);

}

}

/*Output

[prat2@localhost Desktop]$ gcc vignere.c

[prat2@localhost Desktop]$ ./a.out

Enter the length of the key stream. 6

Enter the length of the plain text stream.(Without spaces) 14

Enter the Key. pascal

Enter the Plain text. sheislistening

18 7 4 8 18 11 8 18 19 4 13 8 13 6 

15 0 18 2 0 11 15 0 18 2 0 11 15 0 

The cipher text is: H H W K S W X S L G N T C G 

*/