029_Enc.c

Go to the documentation of this file.

#include <stdio.h>
 
#define MC 2048
 
int main(int argc, char *argv[])
{
    char str[MC], strE[MC], strD[MC], aux[MC];
    int i, nc, a, ai, b, n;
    a = 17;
//  ai = 49;
    b = 21;
    n = 52;
    i=0;
    do{
        str[i++] = getc(stdin);
    }while(str[i-1]!=10);
    str[i-1] = '\0';
    nc = i-1;
    printf("MSG: %s\n", str);
    for(i=0; i<nc; i++)
        printf("%d ", str[i]);
    printf("\n");
    for(i=0; i<nc; i++)
    {
        aux[i] = str[i]-'A'-6*(str[i]>='a');
        printf("%d ", aux[i]);
    }
    printf("\n");
    for(i=0; i<nc; i++)
    {
        aux[i] = (a*((int)aux[i])+b)%n;
        printf("%d ", aux[i]);
    }
    printf("\n");
    for(i=0; i<nc; i++)
        strE[i] = aux[i]+'A'+6*(aux[i]>(n/2-1));
    strE[nc]='\0';
    printf("%s\n", strE);
    for(i=0; i<nc; i++)
    {
        aux[i] = strE[i]-'A'-6*(strE[i]>='a');
        printf("%d ", aux[i]);
    }
    printf("\n");
    ai=1;
    while(((ai*a)%n)!=1)
        ai++;
    printf("ai = %d\n", ai);
    for(i=0; i<nc; i++)
    {
        aux[i] = (ai*((aux[i]<b)*n+aux[i]-b))%n;
        printf("%d ", aux[i]);
    }
    printf("\n");
    for(i=0; i<nc; i++)
    {
        strD[i] = aux[i]+'A'+6*(aux[i]>25);
        printf("%d ", strD[i]);
    }
    strD[nc] = '\0';
    printf("\n");
    printf("%s\n", strD);
    return 0;
}