Crytped calls through 9600Baud GSM-data connections?

Paul Wouters paul at
Fri Feb 2 20:43:08 CET 2007

On Fri, 2 Feb 2007, Robert Michel wrote:

> Did you discussed OTP, using less mobile device batterypower to add
> to the voicestream to build an encrypted connection between on users
> mobil and his homeserver?

Nope. In general, devices these days have enough cpu power to just do
AES. CPU isn't the limiting factor, latency and/or bandwith are. (for
voice encryption at least)

> I thought about that maybe GSM-data connections with 9600Baud would
> be interesting:
> -would piping through such a connection possible without TCP or other
>  overhead?

If you do a gsm dat call, you can of course run your own protocol like
cryptophone does. But I want to try using just a standard ppp/ipsec
connection. Again, I think devices are fast enough and latency is more
of a problem then bandwidth, so this approach seems much easier to
implement then a custom serial/crypto protocol.

> This GSM data connection is used by every commercial cryptophone
> and avoid the delays of GPRS...

Yes, that is what cryptophone is using.

> PS: I made advertisement on this list for your presentation in Berlin,
>     and that this video is no online - but good that mention that it
>     is online again - it worth for the most here on the list to see it.

I moved some files and removed the ASF file in favour of the mp4 file,
since the ASF file caused a lot of problems for people to get to play.


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