.gitignore

*.o
*.x

Makefile

.PHONY: default clean

# declarations #

### compiler ###
CC = gcc

### compilation flags ###
#CFLAGS = -g -Wall -Wextra -Werror -Wshadow -Wpedantic
CFLAGS = -O3 -lm -Wall -Wextra -Werror -Wshadow -Wpedantic -fopenmp

### objects ###
OBJ = password_compare.o timing.o

### executable ###
EXECUTABLE = timing.x

# targets #

### default target ###
# compile executable
default: $(EXECUTABLE)

### executable target ###
$(EXECUTABLE): $(OBJ)
	$(CC) $(CFLAGS) $(OBJ) -o $(EXECUTABLE)

### objects target ###
# compile C-files without linking to .o (object) files
%.o: %.c
	$(CC) $(CFLAGS) -c $< -o $@

password_compare.o

timing.c

#include <stdio.h>
#include <math.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <omp.h>
#include "timing.h"

#define MAXLEN 4

const char symbols[] = "abcdefghijklmnopqrstuvwxyz"
                       "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
                       /* "0123456789"; */
                       /* "äöü" */
                       /* "!@#$%^&*()-_=+[]{}|/?.,<>;:'\"\\`~" */
                       /* "€´ "; */

void increase_char(uint32_t loc, uint32_t max_len, char str[], uint32_t str_len, const char symbs[], uint32_t symbs_len) {
    if (loc >= max_len)
        return;

    if (str[loc] == symbs[symbs_len - 1]) {
        str[loc] = symbs[0];
        increase_char(loc + 1, max_len, str, str_len, symbs, symbs_len);
    } else {
        // Try next character at this location
        char * ptr_to_char = strchr(symbols, str[loc]);
        str[loc] = *(ptr_to_char+1);
    }
}

int main() {
    size_t symbols_len = strlen(symbols);
    for (uint32_t current_length = 1; current_length <= MAXLEN; current_length++) {
        char test_string[current_length];
        memset(test_string, 'a', current_length);

        uint32_t total_combinations = pow(symbols_len, current_length);
        printf("current_length: %u, symbols_len: %lu, total_combinations: %u\n",
                current_length, symbols_len, total_combinations);

        #pragma omp parallel for
        for (uint32_t num_combination =1; num_combination <= total_combinations; num_combination++) {
            /* printf("Trying: %s\n", test_string); */
            if (password_compare(test_string) != -1) {
                printf("Password is %s", test_string);
            }

            increase_char(0, current_length, test_string, current_length, symbols, symbols_len);
        }

        printf("Unsuccessful :(\n");
    }

    return EXIT_SUCCESS;
}

timing.h

#pragma once

#include <time.h>
#include <stdint.h>

extern int password_compare(const char * password);
uint32_t time_max(const clock_t * arr, uint32_t len);