[asterisk-dev] GSM Encryption

[Hans Witvliet]

On Thu, 2012-10-25 at 12:14 -0700, sab sab wrote:
> Hello,
> 
> I have a question that is troubling me and I don't know where to ask
> it. I posted this question on the asterisk forums but no answer. 
> I have this idea to build a security module based on asterisk and
> raspberry pi to secure GSM calls(not gprs, not 3g etc.) . I know that
> there is an encryption( A5 ) involved that was cracked and so on and I
> want to build a stronger one over it, to secure end to end
> conversations. Basicly I want to build a new module that you can stack
> over chan_mobile( for bluetooth connection to the mobile phone ) that
> offers channel encryption. The fantasy would consist of:
> 
> * authentication( certificates maybe, designated keys probably )
> * encryption
> * voice signaling for plain channel or secure channel link( voice that
> announces the attribute of the link )
> 
> Now I ask you, is this feasible? 
> 

With asterisk anything (*) is possible.

Problem however is the other end, the GSM-handset.
Only option at the moment afaics, is with smart-phones.
There you can install soft-phone-clients, that can do encryption.
Point however is, that con can only make secure call doing data-calls.

"Linphone is now available as an Android application.
This application is available through the Google Market for all people
having an Android phone. It is possible to use linphone on android to
make VoIP calls using wifi or 3G (make sure it is allowed by your
operator before)."

for example: http://www.linphone.org/eng/linphone/news/android.html
This is the first release of linphone on android, and we wish to
continue the development in the coming year to bring many improvements,
including:
      * run as a service to allow to receive calls all the time (not
        just when the application is showed)
      * video support
      * optimize battery savings

Mobile phones interfaces
      * Android application (with video support)
      * iPhone/iPad application (with video support)
      * Blackberry application (no video support yet)

There might be other softphones doing the same trick.

hw