Newbee wants to kick start - second try

Flemming Richter Mikkelsen quatrox at
Sat Apr 26 00:09:04 CEST 2008

On 4/24/08, ramsesoriginal <ramsesoriginal at> wrote:
> On Thu, Apr 24, 2008 at 2:47 PM, Adilson Oliveira
> >  - - I've being reading about a project to implement cryptography on
> >  Openmoko so the calls and text messages can be secured, unfortunately I
> >  forgot the name of the project but I've heard that voice calls can't be
> >  secured like that due limitations on the way GSM work. Is this correct?
> As far as I understood it, a GSoC-Project is a sms middleware, which
> should (theoretically) implement a way to simply encrypt with gpg the
> sms. Phone calls can't be encrypted that easilly because, as far as i
> understood it, the microphone is connected directly to the gsm chip.
> But we have many intelligent people here, so someone will probably
> find a way to do even that.

The microphone is connected to the sound card:)

The reason that encrypted calls over GSM is so difficult, is that the GSM
chip samples and encode the input from the microphone. This coding
is optimized for speach only and does not actually send your speach
over the network, but it breakes the sound up in small parts and
use a lookup table to find something that is more or less similar.
It then sends the table index over the network. The actual sound is never
sent, not even in digital form. This is at least how I remember it

Please don't send me Word or PowerPoint attachments.

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