gistfile1.c

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

int main(int argc, const char **argv) {
    uint32_t check;
    uint32_t i;
    uint8_t digit;
	char key[9];
	uint8_t x;
    char c;

	srand(time(NULL));
	key[8] = '\0';

	uint32_t tries = 0;

	do {
		check = 0xBADBEEF;

		for (i=0; i < 8; i++) {
			x = rand() % 16;

			if (x < 10) {
				c = '0' + (char)x;
			} else {
				c = 'a' + (char)(x - 10);
			}

	        key[i] = c;
	        digit = (uint8_t)c;
	        check += (0x1337B00B * digit);
	    }

	    digit = ((check & 0xFF) / 2) * 2;
		tries++;
	} while (digit != 42);

	printf("Cracked after %d tries\n", tries);
	printf("CDKEY: %s\n", key);
    return 0;
}