/*
 * Version A of the C password example: unseeded rand().
 *
 * Companion to "LLMs Can Write Code, but Cannot Read Your Mind"
 * https://hed.am/briefs/llms-can-write-code-but-cannot-read-your-mind/
 *
 *   cc -O2 -Wall -Wextra -o password-rand password-rand.c
 *   ./password-rand
 *   ./password-rand        # same password, every time
 *
 * The C standard specifies that calling rand() without calling srand() first
 * behaves as though srand(1) had been called. The sequence is therefore the
 * same on every run, determined by the C library rather than by anything in
 * this file. Run the program twice and the same password appears twice. That
 * is the visible defect, and the easy one to catch. password-srand.c corrects
 * it and is still not secure.
 */

// Version A - looks fine, absolutely wrong for security
#include <stdio.h>
#include <stdlib.h>

#define PASSWORD_LENGTH 16
#define CHARSET "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

int main(void) {
    const char charset[] = CHARSET;
    const int charset_size = sizeof(charset) - 1; // exclude null terminator

    for (int i = 0; i < PASSWORD_LENGTH; i++) {
        int index = rand() % charset_size;
        putchar(charset[index]);
    }

    putchar('\n');

    return 0;
}