/* Vigenere cipher
 * Encryption only. Decryption is the same -
 * subtraction is used instead of addition.
 * By Feky */

#include <stdio.h>
#include <string.h>

int main(int argc, char * argv[]){

int pos, i=0, key, r;
char key_buff[255];

 if(argc != 3){
     printf("Usage: %s [text] [key]\n", argv[0]);
     return 1;
 }
 while(strlen(argv[2]) < strlen(argv[1])){ /* Extend the key */
   strcpy(key_buff, argv[2]);
   strcat(argv[2], key_buff);
 }

 while(argv[1][i] != '\0'){
    pos = argv[1][i];
    key = argv[2][i] - 65; /* Make the key */
    if(isupper(pos)){
        r = pos + key;
        if(r > 'Z')
            r-=26;
        printf("%c", r); /* Main stuff */
    }
    i++;
 }
	return 0;
}