cryptback.c

// gcc -o cryptback cryptback.c -lcrypt

#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include <crypt.h>

int
main(void)
{
    unsigned long seed[2];
    char salt[] = "$1$........";
    const char *const seedchars =
        "./0123456789ABCDEFGHIJKLMNOPQRST"
        "UVWXYZabcdefghijklmnopqrstuvwxyz";
    char *password;
    int i;

    /* Generate a (not very) random seed.
       You should do it better than this... */
    seed[0] = time(NULL);
    seed[1] = getpid() ^ (seed[0] >> 14 & 0x30000);

    /* Turn it into printable characters from ‘seedchars’. */
    for (i = 0; i < 8; i++)
        salt[3 + i] = seedchars[(seed[i / 5] >> (i % 5) * 6) & 0x3f];

    /* Read in the user’s password and encrypt it. */
    password = crypt(getpass("Password:"), salt);

    /* Print the results. */
    puts(password);
    return 0;
}