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+++
author = "Maik de Kruif"
title = "Challenge 0 - AdventOfCTF"
date = 2020-12-02T17:20:28+01:00
description = "A writeup for challenge 0 of AdventOfCTF."
cover = "img/adventofctf/f90b2bf3f08ee628c09505ff309018ed.png"
tags = [
"AdventOfCTF",
"challenge",
"ctf",
"hacking",
"writeup",
"web",
]
categories = [
"ctf",
"writeups",
"hacking",
]
+++
- Points: 1
## Description
Do you remember the flag in the teaser website?
## Solution
Sadly, the teaser website isn't online anymore. If only someone kept an archive of the internet. This is where the Wayback Machine on [archive.org](https://archive.org/) comes in handy.
So, let's use the Wayback Machine to get the teaser page. <https://web.archive.org/web/20201112020839/https://adventofctf.com/>
When we take a look at the source html of the page we find the following comment:
```html
<!-- Ceasar worked on this you know. Tk9WSXtIRVlfMVNfVGgxU19AX0ZsYTk/fQ== -->
```
It looks like some encoded string. If you've been doing CTFs for a while you'll probably recognize it's encoded in `base64`. We can use the program `base64` to decode this string.
```bash
> echo "Tk9WSXtIRVlfMVNfVGgxU19AX0ZsYTk/fQ==" | base64 -d
NOVI{HEY_1S_Th1S_@_Fla9?}
```
We found the flag! It's `NOVI{HEY_1S_Th1S_@_Fla9?}`.
This flag can then be submitted for the [challenge](https://ctfd.adventofctf.com/challenges#0-1).