The Barcode challen was one of the first challenges I thought of when I started planning the BSides CTF 2025. It is a simple challenge that introduces participants to barcode analysis and decoding, specifically focusing on Code39 barcodes. However I threw some extra complexity in there to mess with people a bit.

This challenge was the most difficult I created for BSides CTF 2025. I was worried about the difficulty, and it was multiple-intermediate steps in a row without a “checkpoint” to help participants. However I did leave clues but I did not have anyone complete it, so I thought I would write this post to explain the challenge and how to solve it.

Time to create a devblog. Details are in this post.