Encrypted calls - Cryptophone.de protocol

Harald Welte laforge at openmoko.org
Mon Aug 25 08:18:05 CEST 2008

On Fri, Aug 22, 2008 at 08:07:28PM +0300, Mikko Rauhala wrote:
> therefore a couple of weeks ago I took it upon myself to liaise a bit
> with GSMK/cryptophone.de, a German encrypted GSM manufacturer. Their CTO
> Frank Rieger was on holidays, but got back to me recently, in a rather
> helpful tone.

Please note that I'm good friends with Frank Rieger, and many cryptophone/GSMK
guys are members of the Berlin Chaos Computer Club, just like myself (working
for openmoko until 11/2007) and roh + gismo who're still with openmoko.

So there's definitely a lot of shared interest and exchange of information and
ideas going on there ;)

> Yes, GSM data calls cost per minute and are slow, but they have
> guaranteed network resources, a decent round-trip, and still enough
> bandwidth for highly compressed voice streams. As for the cost, it isn't
> necessarily higher than for voice calls (obviously, this is locale- and
> operator-dependent and some operators reportedly make you pay through
> the nose, but that's the way it goes).

The problem is also that CSD calls are started to be phased out.  At least some
new firmware revisions of certian GSM base stations simply don't support this
service type anymore.

so apart from being expensive, at least some operators/countries are falling
off the CSD grid...

- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
Software for the world's first truly open Free Software mobile phone

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