[GSM] Source code of RX-FFT and GSM-Analyzer

Long time ago I coded tools to capture, demodulate, decode and decrypt data from an Software Defined Radio (SDR).
As i dont see any reason to keep it private, i decided to release the source code.

I mainly used a device that is comparable to the USRP, but designed by a friend of mine. Still these tools can work with .cfile that are saved from USRP. There is also a prototypic implementation for the HiQ-SDR device that is not tested a lot.

Playing back a recorded WAV file

Nearly all the code is written by myself with these exceptions that come into my mind right now:
– Viterbi decoder (OpenBTS)
– FireCRC (GNU Radio)
– CryptA5 (Marc Briceno et al)

The two main tools in this project are:
RX-FFT, a windows (DirectX) based broadband FFT visualizer and
GSM-Analyzer that can decode (and with kraken-win32 even decrypt) GSM data live from the air or from/to files

Decoding GSM using RX-FFT and GSMAnalyzer

You may use it for your own projects (non-commercial, commercial) after you informed me about your project.
If you have use for this code, you can also send a “thank you”-donation to [email protected] to show me how much you liked it.

How to use it with USRP .cfile files?
1. Get some information about your used .cfile: crystal frequency: 64MHz, 100MHz,  decimation rate (usually visible in the filename as …_d174_… for decimation rate 174)
2. Select “Open”, “IQ Wave file” in GSM Analyzer
3. If the fields are not correctly autodetected, correct them
4. Go into “Options” and press “A” or “B” in “Burst length correction type”. One of them is the correct one for your provider (O2 sometimes uses B)
5. Press “Play”
6. You should see now all traffic happening on the channel
7. In “Filter” menu select those entries that shall be ignored to prevent flooding the log

Even cracking the Cipher using Kraken is possible

source: http://svn.g3gg0.de/svn/default/trunk/EZ-USB/RX-FFT/
user: rx-fft
pass: rx-fft

it’s on bitbucket: https://bitbucket.org/g3gg0/rx-fft
just like Kraken-win32: https://bitbucket.org/g3gg0/kraken-win32

it’s on bitbucket: GitHub – g3gg0/rx-fft
just like Kraken-win32: GitHub – g3gg0/kraken-win32

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