Introducing FISSURE: A Toolbox For The RF Hacker

No matter what the job at hand is, if you’re going to tackle it, you’re going to need the right kit of tools. And if your job includes making sense out of any of the signals in the virtual soup of RF energy we all live in, then you’re going to need something like the FISSURE RF framework.

Exactly what FISSURE is is pretty clear from its acronym, which stands for Frequency Independent SDR-Based Signal Understanding and Reverse Engineering. This is all pretty new — it looks like [Chris Poore] presented a talk at DEFCON a few weeks back about using FISSURE to analyze powerline communications between semi-trucks and their trailers, and they’ve got a talk scheduled for next month’s GNU Radio Conference as well. We’ve been looking through all the material we can find on FISSURE, and it appears to be an RF hacker’s dream come true. They’ve got a few examples on Twitter, like brute-forcing an old garage door opener with a security code set by a ten-position DIP switch, and sending tire pressure monitoring system (TPMS) signals to a car. They also mention some of the framework’s capabilities on the GitHub README; we’re especially interested in packet crafting for various protocols. The video below has some more examples of what FISSURE can do.

It looks like FISSURE could be a lot of fun, and very handy for your RF analysis and reverse engineering work. If you’ve been using Universal Radio Hacker like we have, this looks similar, only more so. We’ll be downloading it soon and giving it a try, so be on the lookout for a hands-on report.

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DSP Spreadsheet: IQ Diagrams

In previous installments of DSP Spreadsheet, we’ve looked at generating signals, mixing them, and filtering them. If you start trying to work with DSP, though, you’ll find a topic that always rears its head: IQ signals. It turns out, these aren’t as hard as they appear at first and, as usual, we’ll tackle them in a spreadsheet.

What does IQ stand for? The I stands for “in phase” and the Q stands for quadrature. By convention, the I signal is a cosine wave and the Q signal is a sine wave. Another way to say that is that the I and Q signals are 90 degrees out of phase. By manipulating the amplitude of I and Q, you can create complex modulation or, conversely, demodulate signals. We’ll see a spreadsheet that shows that completely next time.

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If The I And Q Of Software Defined Radio Are Your Nemesis, Read On

For those of us whose interests lie in radio, encountering our first software defined radio must have universally seemed like a miracle. Here is a surprisingly simple device, essentially a clever mixer and a set of analogue-to-digital or digital-to-analogue converters, that can import all the complex and tricky-to-set-up parts of a traditional radio to a computer, in which all signal procession can be done using software.

A quadrature mixer. Jugandi (Public domain).
A quadrature mixer. Jugandi (Public domain).

When your curiosity gets the better of you and you start to peer into the workings of a software defined radio though, you encounter something you won’t have seen before in a traditional radio. There are two mixers fed by a two local oscillators on the same frequency but with a 90 degree phase shift, and in a receiver the resulting mixer products are fed into two separate ADCs. You encounter the letters I and Q in relation to these two signal paths, and wonder what on earth all that means.

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