On Tuesday, 26 May 2015, at 1:15 am, Peter Todd wrote:
> On Tue, May 26, 2015 at 12:52:07AM -0400, Matt Whitlock wrote:
> > On Monday, 25 May 2015, at 11:48 pm, Jim Phillips wrote:
> > > Do any wallets actually do this yet?
> > 
> > Not that I know of, but they do seed their address database via DNS, which 
> > you can poison if you control the LAN's DNS resolver. I did this for a 
> > Bitcoin-only Wi-Fi network I operated at a remote festival. We had well 
> > over a hundred lightweight wallets, all trying to connect to the Bitcoin 
> > P2P network over a very bandwidth-constrained Internet link, so I poisoned 
> > the DNS and rejected all outbound connection attempts on port 8333, to 
> > force all the wallets to connect to a single local full node, which had 
> > connectivity to a single remote node over the Internet. Thus, all the 
> > lightweight wallets at the festival had Bitcoin network connectivity, but 
> > we only needed to backhaul the Bitcoin network's transaction traffic once.
> 
> Interesting!
> 
> What festival was this?

The Porcupine Freedom Festival ("PorcFest") in New Hampshire last summer. I 
strongly suspect that it's the largest gathering of Bitcoin users at any event 
that is not specifically Bitcoin-themed. There's a lot of overlap between the 
Bitcoin and liberty communities. PorcFest draws somewhere around 1000-2000 
attendees, a solid quarter of whom have Bitcoin wallets on their mobile devices.

The backhaul was a 3G cellular Internet connection, and the local Bitcoin node 
and network router were hosted on a Raspberry Pi with some Netfilter tricks to 
restrict connectivity. The net result was that all Bitcoin nodes (lightweight 
and heavyweight) on the local Wi-Fi network were unable to connect to any 
Bitcoin nodes except for the local node, which they discovered via DNS. I also 
had provisions in place to allow outbound connectivity to the API servers for 
Mycelium, Blockchain, and Coinbase wallets, by feeding the DNS resolver's 
results in real-time into a whitelisting Netfilter rule utilizing IP Sets.

For your amusement, here's the graphic for the banner that I had made to 
advertise the network at the festival (*chuckle*): 
http://www.mattwhitlock.com/bitcoin_wifi.png

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