#include <stdlib.h>
#include <stdio.h>
#include <time.h>

unsigned int good_random_seed();                       /* Returns a strong random seed that cannot be predicted from system time. */

void test_predictable_seed(){
    int i;
    srand(5);                     /* Not based on system time, but hardcoded: Hardcoded Seed in PRNG warning issued here */
    for (i = 0; i<10; i++){
        printf("%d\n", rand());   /* The same sequence of 10 numbers is printed here every time test_predictable_seed() is called. */
    }

    srand(time(NULL));            /* 'Predictable Seed in PRNG' warning issued here */
                                  /* Depending on your time.h implementation, there may also be a Coercion Alters Value warning:
                                   * this call coerces the time_t returned by time() to unsigned int.
                                   */
    for (i = 0; i<10; i++){
        printf("%d\n", rand());   /* An attacker who knows the approximate date and time of execution has a relatively
                                   * small space of seeds to explore, and so a relatively small set of candidate sequences.
                                   */
    }

    srand(good_random_seed());                         /* ok: seed is not time-derived (or hardcoded) */
    for (i = 0; i<10; i++){
        printf("%d\n", rand());
    }
}