Encrypted GSM phone

Fabio Pietrosanti (naif) lists at infosecurity.ch
Tue Apr 10 07:15:00 UTC 2012

On 4/9/12 11:18 PM, Marek Stopka wrote:
> Hi,
> I have been just wondering... would it be possible to use your project
> as a base for DIY encrypted cellphone? My idea is that if I could get
> hold to output data after voice is encoded by GSM EFR codec, I might
> just easily encrypt this digital stream using AES128 and build trully
> encrypted cellphone.
> Where does actual "analog voice from microphone to digital data"
> conversion happends? In a layer1 that runs in a chip, or layer23 that
> runs on a PC? If it would be in layer23, encrypting a data stream with
> AES 128 whould be doable, am I missing something?

Yeah, it has been discussed in this thread:

It would be really nice if you would make some experiment and post the
patch and result.

Especially it would be nice to know the experience when there is
transcoding and when there's no-transcoding between various operator.

It would be very nice to have a 13kbit/s raw channel to be used to
transport encrypted AMR 4.75 audio samples :-)


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