Challenge Description
I wanted to make a CTF challenge based on one of my favorite comic strips, but there wasn’t much to go off of. I ended up making a kinda dusty looking crypto challenge, can you figure out what it’s saying?
P.S. sorry my brackets look kinda bad, they aren’t in the original cipher
Initial Analysis
The challenge provides a PNG image file (pigpen.png) that appears to contain encoded text. The description mentions “brackets look kinda bad, they aren’t in the original cipher,” which is a strong hint that this involves the Pigpen cipher.
Understanding the Pigpen Cipher
The Pigpen cipher (also known as the Masonic cipher or Freemason’s cipher) is a geometric simple substitution cipher that replaces letters with symbols based on their position in a grid. The traditional Pigpen cipher uses a specific pattern. Each letter is replaced by the shape of the “pen” (enclosure) around it in the grid.
Pigpen Cipher Key
By Anomie – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4219969
The key above shows the standard Pigpen cipher mapping where:
- First grid (A-I): Letters are represented by corner/edge shapes without dots
- Second grid (J-R): Letters are represented by corner/edge shapes with one dot
- Third grid (S-V): Letters are represented by diagonal patterns without dots
- Fourth grid (W-Z): Letters are represented by diagonal patterns with one dot
Challenge Analysis
Looking at the provided pigpen.png image, we can see it contains encoded text using what appears to be a version of the Pigpen cipher with extra { and } characters.
Solution Approach
The first step is to carefully examine the PNG image and extract all the Pigpen symbols. Since this is a visual challenge, we need to:
- Identify each unique symbol in the image
- Map them to their corresponding letters based on the Pigpen cipher pattern
- Decode the message
Decoding and Getting the Flag
By carefully examining the symbols in the image and mapping them to the Pigpen cipher grid, we can decode the hidden message:
METACTF{COMICALLYDECODED}