Safe Opener


By: Jonawhogood

Tags: Rev PicoCTF-2022

Problem Description:

Can you open this safe? I forgot the key to my safe but this program is supposed to help me with retrieving the lost key. Can you help me unlock my safe? Put the password you recover into the picoCTF flag format like: picoCTF{password}

When you open the .java file, you see this code:

import java.io.*;
import java.util.*;  
public class SafeOpener {
    public static void main(String args[]) throws IOException {
        BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
        Base64.Encoder encoder = Base64.getEncoder();
        String encodedkey = "";
        String key = "";
        int i = 0;
        boolean isOpen;

        while (i < 3) {
            System.out.print("Enter password for the safe: ");
            key = keyboard.readLine();

            encodedkey = encoder.encodeToString(key.getBytes());

            isOpen = openSafe(encodedkey);
            if (!isOpen) {
                System.out.println("You have  " + (2 - i) + " attempt(s) left");
    public static boolean openSafe(String password) {
        String encodedkey = "cGwzYXMzX2wzdF9tM18xbnQwX3RoM19zYWYz";

        if (password.equals(encodedkey)) {
            System.out.println("Sesame open");
            return true;
        else {
            System.out.println("Password is incorrect\n");
            return false;

The password you entered is first encoded by something called encoder and then compared to the encodedkey. The encoder is a base64 encoder as stated in the first few lines of the code, so then you just use a base64 decoder and decode the encoded key.

Flag: picoCTF{pl3as3_l3t_m3_1nt0_th3_saf3}