picoCTF 2019 Based Writeup

Based is a General Skills challenge worth 200 points.

Description

To get truly 1337, you must understand different data encodings, such as hexadecimal or binary. Can you get the flag from this program to prove you are on the way to becoming 1337? Connect with nc jupiter.challenges.picoctf.org 29956.

Solution

Connecting to this service with netcat, I was asked to convert some binary to “a word”. I figured this meant ASCII. I used CyberChef to convert this string of 1s and 0s to a word.

Next, it gave me some numbers which I assumed were charcodes, but decoding with CyberChef yielded gibberish. The next logical choice was to try to decode these numbers as octal, which worked.

My time ran out, so I had to try this again. I connected a couple more times, and it gave me a different string to decode each time for binary and octal, and finally hexadecimal. It was always in the same order: binary, octal, hex.

I left some open browser tabs with my basic CyberChef recipes to copy/paste these values into, hoping that this wasn’t like other similar CTF challenges that make you write a script in order to overcome the time limit. Luckily, 45 seconds was plenty of time, and I did not have to write a script.

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