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[liberationtech] Open-source GSM network update

Katrin Verclas katrin at mobileactive.org
Tue Jun 21 13:51:35 PDT 2011


You bet. We are ordering the equipment next week and then install day maybe middle of July?  We are game - we want to run this baby some more. 

Katrin 

On Jun 21, 2011, at 4:45 PM, Daniel Bryg wrote:

> Hi Nathan and others,
> 
> Thank you for putting on the hackday and raising the issues arising from that 
> session here in this thread. Apologies for not getting back to the list sooner.
> 
> The default firewall settings on OpenWRT, separate from Tor settings, allow for 
> LAN->WAN forwarding and that's what likely was in that router (Nathan, perhaps 
> you can verify this in the 'config forwarding' section of 
> /etc/config/firewall). 
> Add the fact that we noticed a surprisingly short delay in the call, and it 
> suggests there was no additional TCP wrapping for Tor on the FreeSwitch or 
> wherever and the calls indeed went out bypassing Tor which doesn't proxy UDP. 
> So, Nathan, how do the sip calls go out from the phones with Orbot?
> 
> As Moxie notes this is an issue that is unlikely to be solved by stuffing one's 
> Christmas stocking with RTP inside TCP inside Tor as doing so would leave 
> precious little room left in the stocking for actual presents!
> 
> We are left with some outstanding questions. Can we re-create and verify what 
> occurred in the lab last week? Can UDP be fully implemented within Tor? What 
> does other current technology such as Skype do when UDP is not available? We 
> would love to get back into the lab to approach these questions and issues. Is 
> there any chance of scheduling another day with the equipment in the Open 
> Mobile 
> Lab? If not then perhaps we can organize another hackday in the Access office.
> 
> Thanks, 
> Daniel
> Access
> 
> 
> ----- Original Message ----
> From: Nathan of Guardian <nathan at guardianproject.info>
> To: liberationtech at lists.stanford.edu
> Sent: Mon, June 20, 2011 11:41:10 PM
> Subject: Re: [liberationtech] Open-source GSM network update
> 
> On 06/20/2011 08:26 PM, Moxie Marlinspike wrote:
>> But based on the acrobatics we go through to get
>> encrypted VoIP working acceptably over low-latency UDP links, I imagine
>> that RTP over TCP alone would be mostly unusable, and that RTP over TCP
>> over Tor would probably just be totally fucked.
> 
> It would sound like that moment where Neo enters the Matrix for the
> first time (queue sound fx "mwwwwmwwaaaaaaaoaaawwwrrrrr."), or perhaps
> slightly better than the first telephone call ever made. Regardless, I
> think the last thing that Tor needs (at least for now) is a ton of
> people making onion-routed telephone calls.
> 
> Fortunately, from my initial, limited experience with this system
> (OpenBTS+USRP->Freeswitch->over BGAN, ->over Tor, etc), it seems like
> the idea that you could drop a suitcase setup in somewhere, flip it on,
> and tell everyone to go crazy making free phonecalls to Al Jazeera
> hotlines is not a very feasible idea. Well, at least to sound slightly
> more positive, the issue of scalability of voice applications,
> particularly in these super dynamic contexts, needs to be seriously
> investigated.
> 
> What could work though is SMS, perhaps MMS (if GPRS support existed), as
> it is asynchronous (perfect for Tor), easier to scale on a limited
> amount of hardware, cost effective (more on that later), and it all runs
> over the SIP channel via TCP, if I am not mistaken. We even tested
> TextSecure in this setup (sorry that wasn't mentioned earlier), and it
> worked great, defeating any of the SIP/UDP keyword packet filtering we
> attempted, for obvious reasons, though it was cool to watch the OTR
> handshaking happen from the inside out.
> 
> Back to the pricing thing, it is said that typical SMS costs $1310/MB
> (http://en.wikipedia.org/wiki/Text_messaging#Pricing_concerns), so
> paying for the $5/MB cost of routing SMS over BGAN seems like an
> insanely great deal.
> 
> Best,
> Nathan
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Katrin Verclas
MobileActive.org
katrin at mobileactive.org

skype/twitter: katrinskaya
(347) 281-7191

A global network of people using mobile technology for social impact
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