Encrypted calls - Cryptophone.de protocol

Mikko Rauhala mjrauhal at cc.helsinki.fi
Mon Aug 25 17:41:28 CEST 2008

Quoting Harald Welte <laforge at openmoko.org>:
> On Fri, Aug 22, 2008 at 08:07:28PM +0300, Mikko Rauhala wrote:
> > 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

Yeah well. :) I had tried to keep tabs on what all was going on with
encrypted call support discussion 'round here; perhaps I've missed
something, perhaps just not all of the data was made available on these
lists, but it was clear from some IRC and E-mail discussions that others
were unclear on the cryptophone protocol etc. situation as well, so at least
hopefully my inquiry and subsequent report was of some utility in further
spreading the information :]

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

That's good.

> 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.

That's a bummer, though. Still, hopefully it shan't deter sh from continuing
with his project to implement encrypted CSD calls - it can still be relevant
in many parts of the world for a good while, and really, aside from
push-to-talk GPRS, is the only sanish way to do it with the current hardware
(when utilizing the cell network, that is).

As a purely anecdotal data point my operator, Saunalahti, in Finland, does
offer this service - or at least it's in their price list, I haven't tried
it in practice recently ;) The costs aren't even very prohibitive, though
noticably higher for the receiving party.

For an outgoing 9k6 data call the charges are the same as for a normal voice
call except for a 0.12 euro extra charge per call (not per minute). However,
for the recipient the call will be more expensive - 0,27 euros a minute,
more than double the caller's rate (depending slightly on their exact plan).
Note that around here, you don't pay to receive usual voice calls. The
service is clearly seen as something they can get a premium on. (Makes one
wonder about a feature where you use an out of band method - like an SMS -
to communicate your desire to initiate a call, and then both phones call out
to a relay service ;)

Aaaanyway, yeah. I'll get me coat now. Cheerio and all.

Mikko Rauhala   - mjr at iki.fi     - <URL:http://www.iki.fi/mjr/>
Transhumanist   - WTA member     - <URL:http://www.transhumanism.org/>
Singularitarian - SIAI supporter - <URL:http://www.singinst.org/>

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