baby

Welcome to this year's RF category! Here's the usual legal disclaimer yada yada:

We are not lawyers. We're not your lawyers. This isn't legal advice.

When playing with radios, never transmit unless you know what you're doing. Always check your local laws and legislations before you transmit. In the United States, unauthorized transmission outside of certain frequency bands is illegal and can even be considered a felony offense in some cases. Radio frequency is cool, but don't get in trouble!

You do not need to transmit for any of these challenges. You do not need any radio hardware for any of these challenges. All of these challenges were made to be solved without the need for real-life hardware.

This disclaimer isn't meant to deter. It's meant to educate and communicate that you should educate yourself on the specific legalities for your locality if you want to dive into the world of RF. Once again, this is not legal advice, and you do not need to transmit for any of these challenges.

Now that we've gotten that out of the way, let's start with a simple challenge to prove some basic competency before we get into the more advanced stuff. This challenge will unlock the rest of the RF category.

I picked up this transmission, but it's way too noisy to make any sense of it. Can you give it a shot?

Flag format: irisctf{th3_m3ss4ge} in all lowercase. Replace spaces with underscores. Add curly braces.

dotdotdot.tar.gz

By: skat

easy

"I found this radio station on the Internet."

"Like they continuously stream songs on YouTube or something?"

"No, it's like... a radio station, and they play... Well, it's hard to explain."

nc rfoip-620ac7b1.radio.2025.irisc.tf 6531

By: skat

medium

While browsing the radio spectrum, I found this interesting radio channel on 434.677 MHz with some intermittent activity. I'm having some trouble making sense of it, but I'm fairly certain that this is being used as some sort of communications channel. Can you find out what's being transmitted?

Note: while not required, it's highly recommended that you do RFoIP before you do this challenge. This challenge is a bit more difficult than RFoIP, and RFoIP will give you a good foundation for understanding this challenge.

nc sinefm-f94347f3.radio.2025.irisc.tf 6531

By: skat

medium

All the kids are using this Spicy Messaging Sinusoids thing nowadays. Nobody speaks to each other anymore!

spicy-messaging-sinusoids.tar.gz

By: skat