Lion Cipher Lab
Decode a digital radio protocol with Universal Radio Hacker (no radio required)
- Foundations
- Intermediate
- ~60 min
- Free · no account required
Why it matters
Tools like rtl_433 feel like magic: point them at a radio recording and out pops a temperature and a device ID. That magic is a stack of steps — demodulation, bit timing, decoding — that the tool does for you, and the moment you meet a device rtl_433 has never heard of, the magic stops and you have to do those steps yourself. This lab makes that hidden layer concrete by running it backwards and forwards on a signal you build from scratch: you turn a handful of bits into an actual modulated radio wave, then turn that wave back into the same bits. Once you have watched a bitstream become a…
What you'll learn
- what radio modulation is (ASK/OOK vs FSK) and why signals must be demodulated
- reading IQ / complex-sample files as the raw record of a radio wave
- what samples-per-symbol means and how it sets the bit timing
- encoding a bitstring into a modulated signal in URH's Generator
- loading a signal and letting URH auto-detect the modulation and demodulate it in the Interpretation tab
- confirming a recovered bitstream maps back to the original message
- the judgment of when to reach for URH vs a ready-made decoder like rtl_433
- the legal/ethical line between analyzing your own signal and transmitting on real frequencies
Steps in this lab
- What modulation is, and why a wave has to be 'decoded' at all
- Install Universal Radio Hacker (URH)
- Open the Generator and type your packet's bits
- Set the modulation to ASK/OOK and choose samples-per-symbol
- Export the generated signal as an IQ (.complex) file
- Load the file back and let URH demodulate it
- Confirm you recovered the original message
- When to reach for URH, when for a ready-made decoder — and how a pro captures for real
- The line you do not cross — analyze your own signal, don't transmit